fix(security): scope the filesystem path picker per user in multi-user mode

Both picker endpoints are a second file-serving surface, and they
inherited neither the attachment guard's confinement nor its ownership
scoping. Two separate holes:

1. `sessionId` contributes that session's workingDir as a browse root,
   but it was resolved straight off ctx.sessions/ctx.store with no owner
   check, unlike the nine other session-scoped handlers in this file. A
   non-admin could pin ANOTHER user's working directory as a root just
   by passing their session id, then list and preview underneath it. Now
   runs canAccessOwned and reports 404, which also avoids confirming
   that a session id exists.

2. `Home` and `CASES_DIR` were unconditional roots for every caller.
   Per-user spaces live at <USER_SPACES_DIR>/<username>, which is INSIDE
   homedir(), so the Home root alone exposed every other user's
   workspace. A multi-user non-admin now gets only their own
   userSpacePath plus anything explicitly listed in
   CODEMAN_FILE_PICKER_ROOTS. /mnt/d is dropped as well: a broad host
   mount should be an explicit operator decision in a multi-user
   deployment, and operators who want it can name it in that env var.

Admins and single-user mode keep the host-wide roots, so behavior is
unchanged unless CODEMAN_MULTIUSER is on (opt-in, off by default).

All three discriminating tests were verified to fail against the
previous code: browse and preview both returned 200 instead of 404, and
the roots came back as [Home, Codeman Cases, ...] instead of [My Space].
Full suite green, 3784 passed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/architecture-invariants.md

@@ -80,6 +80,13 @@ Implementation detail extracted from `CLAUDE.md` so that file stays small enough
 
 ⚠️ **This is a second file-serving surface, so it carries the same confinement burden as [Attachments](#attachments) and does not inherit it automatically.** Traversal is allowlisted to Home, `CASES_DIR`, `/mnt/d`, or extra roots explicitly configured via `CODEMAN_FILE_PICKER_ROOTS`; sensitive trees are blocked and symlink escapes are rejected after `realpath` resolution rather than before. Without the realpath step a symlink inside an allowed root would walk straight out of it. `preview` reuses the shared conversion cache and the **global** `document-conversion-limiter`, which is what stops N concurrent large-document previews from forking N multi-minute converter processes. Content types are pinned: images and PDF inline, DOCX/PPTX through the converters, and Markdown/TXT/JSON as inert `text/plain` (never `text/html`, which would be stored XSS on our own origin). Size caps are 2MB for text and 50MB for binary/document previews.
 
+⚠️ **Ownership scoping is also not inherited, and both endpoints must do it themselves.** Two separate holes shipped in the original version and are now regression-guarded in `test/routes/file-routes.test.ts`:
+
+1. The optional `sessionId` param adds that session's `workingDir` as a "Current Folder" root. It is looked up directly off `ctx.sessions`/`ctx.store` rather than through `findSessionOrFail`, so the `canAccessOwned` check has to be written out by hand. Without it a multi-user caller pins **another user's** working directory as a browse root just by passing their session id. It reports 404 rather than 403 so the endpoint does not confirm that a session id exists.
+2. `Home` and `CASES_DIR` were unconditional roots. Per-user spaces live at `<USER_SPACES_DIR>/<username>`, which is **inside `homedir()`**, so a `Home` root alone let any authenticated user browse and preview every other user's workspace. In multi-user mode a non-admin now gets only `My Space` (their own `userSpacePath`) plus anything in `CODEMAN_FILE_PICKER_ROOTS`; `/mnt/d` is dropped too, since a broad host mount should be an explicit operator decision in a multi-user deployment. Admins and single-user mode keep the host-wide set unchanged.
+
+The general rule: **any new endpoint that turns a caller-supplied `sessionId` into a filesystem path is an ownership boundary**, whether or not it goes through `findSessionOrFail`.
+
 ### Ultracode and workflow-run visualization
 
 **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`.