fix(multiuser): close cross-user web-layer scoping holes found in review

The opt-in multi-user feature's only enforcement is web-layer scoping
(all sessions share one OS account). An adversarial review found 8 critical
+ 7 high cross-user holes that defeated it, plus mediums; all fixed here.
Single-user (flag-off) behavior stays byte-identical apart from documented
consistency deltas.

Ownership / confinement:
- DELETE /api/sessions (bulk) + /:id now owner-scope / findSessionOrFail
- quick-start, cron (create+fire), scheduled runs confine workingDir to the
  owner's space; case link/docker-link/docker-import confine the host path
- resolveCasePath no longer resolves linked cases for non-admins; foreign
  remote/docker cases are skipped (fall through to the caller's own local case)
- history, subagents/workflows, mux-sessions, orchestrator, cron run-history,
  away-digest, and remote/docker host reads are owner- or admin-scoped

Permission policy (section 6.3):
- non-granted users are downgraded at every spawn site incl. legacy
  /api/scheduled, PlanOrchestrator one-shots, remote launch, and the cron-fire
  gemini/codex bypass switches; resolveClaudeModeForUsername now fails closed

Auth / store:
- verify-first login throttle (a correct password is never locked out),
  /ws terminal subject to the change-password lockbox, cookie fast-path
  re-validates identity live, role/grant changes revoke sessions, admin delete
  runs the last-admin guard before any teardown
- users.json: distinguish missing (ENOENT) from corrupt/unreadable so a bad
  read can't overwrite all accounts; unique per-process temp write path

Event streams:
- debounced session:updated + batched task:updated, clipboard, and push
  notifications route by owner (fail closed); getLightState hides machine-wide
  globalStats from non-admins

Tests: two suites updated to assert the fixed (secure) behavior. tsc, eslint,
and test:ci all green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -192,11 +192,11 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 
 **Attachments** (live external document references; COD-37/#119 core, COD-38/#120 previews, COD-39/#121 history): all wiring in `file-routes.ts`. **Registry** (`attachment-registry.ts`): an **in-memory** map of a stable `attachmentId` → an absolute, `realpath`-resolved, extension-allowlisted file path, so browser requests (`GET /api/sessions/:id/attachments/:attachmentId/raw`) never carry arbitrary absolute paths; `POST /api/sessions/:id/attachments` registers one. **Magic links** (`attachment-magic.ts`): parses `codeman://attach?...` out of terminal output — ⚠️ this scanner is prompt-injectable, so the scan path is **force-confined to the session workspace** (a hostile prompt could otherwise make it read arbitrary host files over SSE); emits the `attachment:detected` SSE event. Security gate is an extension **allowlist** (`isSupportedAttachmentExtension`, in the registry/magic modules), not a blocklist; a separate path layer (`config/attachment-guard.ts`) confines reads to the workspace (`attachmentConfineToWorkspace`) and blocks sensitive trees (`/root`, `/etc`). **Previews + thumbnails** (COD-38): `:attachmentId/preview` + `:attachmentId/thumbnail` (and the workspace-file equivalents `file-preview`/`file-thumbnail`) render Office docs/PDFs via external converters (`pdftoppm` / LibreOffice `soffice` / Word-COM `powershell`); `document-preview-cache.ts` is a shared disk cache (de-dups _identical_ in-flight inputs), `document-thumbnailer.ts` does best-effort first-page images, and `document-conversion-limiter.ts` is a **global converter-spawn concurrency cap** (`runWithConversionLimit`) — without it, N distinct large docs detected at once fork N multi-minute converter processes = a localhost fork-bomb-shaped resource-exhaustion vector. **History drawer** (COD-39): `session-attachment-history.ts` tracks the last `ATTACHMENT_HISTORY_LIMIT` (100) attachments per session (`Session._attachmentHistory`, persisted via `SessionState.attachmentHistory`, replayed so externals re-register on reconnect); `GET /api/sessions/:id/attachments` is the list endpoint. ⚠️ The history drawer's launcher button is desktop-only — hidden on phones (regression-guarded; see `mobile-header-buttons-policy` test). Session-local files keep using the existing workspace-scoped `file-routes` paths; the registry is only for explicit live externals. **Codex generated artifacts** (COD-166/#150, `generated-artifact-attachments.ts`): codex-mode sessions ALSO scan (ANSI-stripped) output for `Saved to: file:///…` lines and surface those files as attachment cards with a relaxed trust policy — the allow decision runs on the **realpath-resolved** path against `os.homedir()`-anchored `~/.codex` marker dirs (symlink escapes fall back to force-confinement); gated to `mode === 'codex'` only (`source` is a REQUIRED param through the listener-deps chain — a dropped arg here silently kills the feature). Image thumbnails pass through jpg/jpeg/gif/webp.
 
-**Ultracode / Workflow-run visualization** (opt-in `showUltracodeAgents`, default OFF; released 1.1.2): the Workflow tool ("ultracode") writes a COMPLETION artifact per run at `~/.claude/projects/<projHash>/<sessionUuid>/workflows/wf_*.json` (written only at run end); LIVE in-flight runs exist only as transcript dirs at `…/subagents/workflows/wf_<id>/` (journal.jsonl + agent-_.jsonl). `workflow-run-watcher.ts` (STANDALONE — deliberately never imports/touches `subagent-watcher.ts`; separate singleton, though it independently reads the same `subagents/workflows/` tree) scans BOTH sources via periodic poll + per-directory chokidar watchers with per-source mtime skip (LRU agentStatCache + journalCache), synthesizing ACTIVE runs (live per-agent tokens/tools/state from transcripts, title/phases from the workflow script) until the completion `wf\__.json`appears and supersedes, and broadcasts SSE`workflow:run_discovered`/`run_updated`/`run_removed`. The watcher is started when **either** `showUltracodeAgents`**or**`ultracodeFloatingWindows` is on (`server.ts` `isWorkflowAgentTrackingEnabled()`returns`(showUltracodeAgents ?? false) || (ultracodeFloatingWindows ?? false)`). Served via `GET /api/workflows`(optional`?minutes=`filter) and`GET /api/workflows/:runId`. Frontend `ultracode-panel.js`renders a docked master-detail view (LEFT: runs + phases; RIGHT: per-agent tokens + tool-calls; click an agent card → its live transcript via client-side`agentId`join). **Additionally**,`ultracode-windows.js`auto-pops a draggable **floating window per active run** (gated on a **DEDICATED**`ultracodeFloatingWindows`toggle, default OFF — independent of the dock panel's`showUltracodeAgents`; see `\_ultracodeFloatingEnabled()`), connected by a glowing line to the originating session tab (resolved by `session.claudeSessionId === run.sessionUuid`) — same line idiom as subagent windows, drawn into the shared `#connectionLines`SVG from the tail of`\_updateConnectionLinesImmediate`. The window auto-closes ~8s after its run finishes; explicit dismissals are remembered. Clicking an agent card opens an **in-page** connected transcript window (not a browser popup); both run and transcript windows minimize **into** the originating session tab as a merged `ULTRA`badge (🧬 runs / 📄 transcripts) with a restore/dismiss dropdown — minimized runs are skipped by auto-pop. Gesture beta: floating subagent/ultracode windows are pinch-draggable (a`window`grab kind in`entry.ts`). Types: `src/types/workflow-run.ts`. Config: `src/config/workflow-config.ts`.
+**Ultracode / Workflow-run visualization** (opt-in `showUltracodeAgents`, default OFF; released 1.1.2): the Workflow tool ("ultracode") writes a COMPLETION artifact per run at `~/.claude/projects/<projHash>/<sessionUuid>/workflows/wf_*.json` (written only at run end); LIVE in-flight runs exist only as transcript dirs at `…/subagents/workflows/wf_<id>/` (journal.jsonl + agent-\_.jsonl). `workflow-run-watcher.ts` (STANDALONE — deliberately never imports/touches `subagent-watcher.ts`; separate singleton, though it independently reads the same `subagents/workflows/` tree) scans BOTH sources via periodic poll + per-directory chokidar watchers with per-source mtime skip (LRU agentStatCache + journalCache), synthesizing ACTIVE runs (live per-agent tokens/tools/state from transcripts, title/phases from the workflow script) until the completion `wf\__.json`appears and supersedes, and broadcasts SSE`workflow:run_discovered`/`run_updated`/`run_removed`. The watcher is started when **either** `showUltracodeAgents`**or**`ultracodeFloatingWindows` is on (`server.ts` `isWorkflowAgentTrackingEnabled()`returns`(showUltracodeAgents ?? false) || (ultracodeFloatingWindows ?? false)`). Served via `GET /api/workflows`(optional`?minutes=`filter) and`GET /api/workflows/:runId`. Frontend `ultracode-panel.js`renders a docked master-detail view (LEFT: runs + phases; RIGHT: per-agent tokens + tool-calls; click an agent card → its live transcript via client-side`agentId`join). **Additionally**,`ultracode-windows.js`auto-pops a draggable **floating window per active run** (gated on a **DEDICATED**`ultracodeFloatingWindows`toggle, default OFF — independent of the dock panel's`showUltracodeAgents`; see `\_ultracodeFloatingEnabled()`), connected by a glowing line to the originating session tab (resolved by `session.claudeSessionId === run.sessionUuid`) — same line idiom as subagent windows, drawn into the shared `#connectionLines`SVG from the tail of`\_updateConnectionLinesImmediate`. The window auto-closes ~8s after its run finishes; explicit dismissals are remembered. Clicking an agent card opens an **in-page** connected transcript window (not a browser popup); both run and transcript windows minimize **into** the originating session tab as a merged `ULTRA`badge (🧬 runs / 📄 transcripts) with a restore/dismiss dropdown — minimized runs are skipped by auto-pop. Gesture beta: floating subagent/ultracode windows are pinch-draggable (a`window`grab kind in`entry.ts`). Types: `src/types/workflow-run.ts`. Config: `src/config/workflow-config.ts`.
 
 **Cross-session search** (COD-113/#133): `GET /api/search?q=&types=&limit=` federates an **in-memory** search across all live sessions — session metadata (name/workingDir/id), run-summary events, and per-session attachment-history file entries (workspace-relative path only; the server-private `externalPath` is never read). Pure core `searchSources()` in `search-service.ts` (substring-matches with hard per-type caps — no regex, so no ReDoS; no filesystem reads, so no traversal); `harvestSources()` in `search-routes.ts` gathers the in-memory sources. `SearchQuerySchema` bounds `q` (1–200), allowlists `types` (`session,event,file`), clamps `limit` (1–60). Returns the `{success,data}` envelope. Frontend: history-panel search box in `terminal-ui.js`. Types: `src/types/search.ts`.
 
-**Multi-user mode** (opt-in `--multiuser` / `CODEMAN_MULTIUSER=1`, OFF by default; branch `feat/multiuser-mode`, design `docs/multi-user-plan.md`): named users with individually scrypt-hashed passwords in `~/.codeman/users.json` (via `src/user-store.ts`: atomic 0600 write, short-TTL cache, SERIALIZED read-modify-write so a fire-and-forget `touchLastLogin` can't clobber a concurrent route write, last-admin invariants). Gated everywhere by `isMultiUserMode()` (`src/config/multiuser.ts`); when OFF, behavior is byte-identical to single-user (all scoping helpers short-circuit). ⚠️ **Not a security boundary at the agent layer** — every session still runs as the SAME OS account; this separates WORKSPACES, it does not sandbox users (Docker cases are the isolation story). Auth: a PARALLEL async branch in `middleware/auth.ts` (single-user branch untouched) verifies `username:password` against the store, mints identity-carrying cookies (`AuthSessionRecord` gains `username`/`role`/`mustChangePassword`), decorates `req.authUser` (Fastify augmentation; single-user leaves it undefined and the ownership helpers default to a synthetic admin), enforces a per-username failure bucket + the `mustChangePassword` lockbox. Ownership threads through `Session.owner` (stamped from `req.authUser`/`job.owner` at every `new Session()`, round-tripped via `MuxSession.owner` on recovery); `findSessionOrFail(ctx,id,req)` does a NOT_FOUND owner check; list endpoints + `getLightState` + SSE (`deriveSseHint` routes session-scoped events by owner, fail-closed; machine-level + host-plan telemetry admin-only) + WS + search + file-preview all filter by owner. §6.3 permission policy: non-granted users are forced to `--permission-mode auto` (via `resolveClaudeModeForUser` at all spawn sites, incl. one-shots because `buildPromptArgs` now respects the session mode), and shell mode / cron `launchCommand` require the `canBypassPermissions` grant. Cases live in per-user `~/codeman-users/<name>/cases` (`resolveCasesDir`); a non-admin's `workingDir` is realpath-confined there; host CRUD is admin-only. Admin API `src/web/routes/admin-routes.ts` (`/api/admin/users*`, one-time passwords, audit log `admin-audit.jsonl`) + self-service `/api/me` + `/api/me/password` (`me-routes.ts`); frontend `public/admin-ui.js` (identity boot, change-password modal + interceptor, admin Users tab). CLI `codeman users add|passwd|list|rm`. Per-user session cap via `assertSessionCapacity`/`sessionCapacityMessage`. Tests: `test/user-store.test.ts`, `test/multiuser-auth.test.ts`, `test/ownership-scoping.test.ts`, `test/admin-routes.test.ts`, `test/admin-ui.test.ts`.
+**Multi-user mode** (opt-in `--multiuser` / `CODEMAN_MULTIUSER=1`, OFF by default; branch `feat/multiuser-mode`, design `docs/multi-user-plan.md`): named users with individually scrypt-hashed passwords in `~/.codeman/users.json` (via `src/user-store.ts`: atomic 0600 write, short-TTL cache, SERIALIZED read-modify-write so a fire-and-forget `touchLastLogin` can't clobber a concurrent route write, last-admin invariants). Gated everywhere by `isMultiUserMode()` (`src/config/multiuser.ts`); when OFF, behavior is byte-identical to single-user (all scoping helpers short-circuit). ⚠️ **Not a security boundary at the agent layer** — every session still runs as the SAME OS account; this separates WORKSPACES, it does not sandbox users (Docker cases are the isolation story). Auth: a PARALLEL async branch in `middleware/auth.ts` (single-user branch untouched) verifies `username:password` against the store, mints identity-carrying cookies (`AuthSessionRecord` gains `username`/`role`/`mustChangePassword`), decorates `req.authUser` (Fastify augmentation; single-user leaves it undefined and the ownership helpers default to a synthetic admin), enforces a per-username failure bucket + the `mustChangePassword` lockbox. Ownership threads through `Session.owner` (stamped from `req.authUser`/`job.owner` at every `new Session()`, round-tripped via `MuxSession.owner` on recovery); `findSessionOrFail(ctx,id,req)` does a NOT_FOUND owner check; list endpoints + `getLightState` + SSE (`deriveSseHint` routes session-scoped events by owner, fail-closed; machine-level + host-plan telemetry admin-only) + WS + search + file-preview all filter by owner. §6.3 permission policy: non-granted users are forced to `--permission-mode auto` (via `resolveClaudeModeForUser` at all spawn sites, incl. one-shots because `buildPromptArgs` now respects the session mode), and shell mode / cron `launchCommand` require the `canBypassPermissions` grant. Cases live in per-user `~/codeman-users/<name>/cases` (`resolveCasesDir`); a non-admin's `workingDir` is realpath-confined there; host CRUD is admin-only. Admin API `src/web/routes/admin-routes.ts` (`/api/admin/users*`, one-time passwords, audit log `admin-audit.jsonl`) + self-service `/api/me` + `/api/me/password` (`me-routes.ts`); frontend `public/admin-ui.js` (identity boot, change-password modal + interceptor, admin Users tab). CLI `codeman users add|passwd|list|rm`. Per-user session cap via `sessionCapacityState`/`sessionCapacityMessage`. Tests: `test/user-store.test.ts`, `test/multiuser-auth.test.ts`, `test/ownership-scoping.test.ts`, `test/admin-routes.test.ts`, `test/admin-ui.test.ts`.
 
 **Away digest** (COD-41/#136): `GET /api/away-digest?range=&since=&until=&lastViewed=` aggregates "what happened while you were away" from the lifecycle log + run-summary events + live sessions + daily token stats + recently-completed subagents into needs-attention/completed/still-running/idle/informational sections. Pure aggregator in `web/away-digest.ts` (`resolveAwayDigestRange()` validates the window — `since-last-visit`/`1h`/`today`/`24h`/`custom`, server-local TZ; `buildAwayDigest()` classifies). Header-button modal in `panels-ui.js` (button hidden on phones — regression-guarded). ⚠️ Returns `{success:true,digest}` (a legacy raw-ish shape, consistent with the other raw GET handlers in `system-routes.ts` — `{entries}`/`{config}`/`{files}`/`getSystemStats()`); frontend + tests read `.digest`. Subagent lookback is a fixed 60-min window regardless of range.