feat(cases): clone a Git repository as a new case (#236)

Adds an Add Case -> "Clone Repo" tab plus two endpoints, implementing
@DodgyBadger's proposal in #236: clone a public repository straight into
codeman-cases/<name> and register it as a normal local case.

POST /api/cases/clone is synchronous by design (request held open, bounded
by GIT_CLONE_TIMEOUT_MS): no job store, no polling, no cancellation
surface. Success broadcasts the usual case:created event, so the case
still appears when a proxy idle-timeout kills the request mid-clone.

POST /api/cases/clone-preflight runs `git ls-remote --symref` so the UI can
say, while the user is still typing, whether the URL is cloneable without
credentials, what its default branch is, and which branches/tags exist.

Core lives in src/git-clone.ts, split into a pure half (URL parse, argv/env,
ls-remote parse, stderr classification) and a thin IO half, so every
security decision is unit-testable without spawning anything:

- `<name>::<payload>` transports are refused as a family, not by name:
  ext:: is the famous one, but any of them dispatches to git-remote-<name>
  and turns a clone into arbitrary command execution.
- A leading `-` is refused AND every spawn puts `--` before the operands.
  Either alone is one edit away from being a hole.
- argv arrays, never a shell. URLs carrying user:password@ are refused.
- gitNonInteractiveEnv() closes all four ways git can block on a prompt
  with no terminal attached (terminal prompt, askpass/GUI, ssh, GCM).
  HOME/PATH stay inherited, so a user's own credential helper or ssh agent
  keeps working; Codeman itself collects and stores nothing.
- The timeout signals the process GROUP, since clone fans out into
  git-remote-https/index-pack children that outlive a signal to the parent.
- Bounded output (redacted stderr tail, capped ls-remote stdout, 500 refs
  each) and a global 2-op pool, so N large clones cannot exhaust the host.

Repository contents beat scaffolding: an existing CLAUDE.md is kept, hooks
are merged into whatever .claude/settings.local.json the repo shipped, and
a repo that ships its own Claude settings is reported back as a warning
(those hooks run locally as soon as a session starts there). A failed clone
removes only the directory the attempt created, and refuses a pre-existing
destination outright, so it can never squat on a case name.

Not admin-gated in multi-user mode, unlike /api/cases/link: it writes only
inside the caller's own case space. Local-path/file:// sources are the
exception and stay admin-only there.

UI: live verdict under the URL field, case name filled from the parsed repo
until the user types their own, branch/tag as a datalist of the remote's
real refs, optional shallow clone, and a Brain picker (installed CLIs only)
that points the Run button at the chosen agent. Starting a session stays
opt-in. The tab hides itself when the server reports no git.

Tests: the pure half exhaustively (every refusal has a case), plus real git
against a real local bare repo for clone/ref/timeout/cleanup, and a
route-level suite with unmocked fs that clones through the endpoint.

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

docs/architecture-invariants.md

@@ -130,6 +130,21 @@ The general rule: **any new endpoint that turns a caller-supplied `sessionId` in
 
 Tests: `test/file-editing-policy.test.ts` (pure policy), `test/routes/file-write-routes.test.ts` (deliberately **unmocked fs** against a real temp workspace — symlink/TOCTOU/mode behavior must be exercised for real).
 
+### Clone a repository as a case
+
+**Clone Repo tab** (issue #236, proposed by @DodgyBadger): `POST /api/cases/clone` clones a public repository into the caller's case space and registers it as a normal local case; `POST /api/cases/clone-preflight` answers "can this be cloned anonymously, and what refs does it have?" while the user is still typing. Core in `src/git-clone.ts`, split into a PURE half (URL parse, argv/env, `ls-remote` parse, stderr classification) and a thin IO half (`probeGitRemote`, `cloneRepository`).
+
+- ⚠️ **The URL is a code-execution surface, which is why it is parsed rather than forwarded.** `ext::sh -c <cmd>` makes git run an arbitrary command as its transport, and ANY `<name>::<payload>` dispatches to a `git-remote-<name>` helper, so every `::` form is refused outright. A repository starting with `-` is read by git as a flag; that is rejected AND every spawn puts `--` before the operands, because either defence alone is one edit away from being a hole. Spawns are argv arrays, never a shell (unlike `remote-hosts.ts`, which does build a shell line and must `shellescape`). The Zod schema deliberately only length-bounds `repository` — a weaker regex duplicate of `parseGitRepositoryUrl` would be the copy that drifts.
+- ⚠️ **Non-interactive or it hangs the request.** The clone is synchronous by design (no job store, no polling, no cancellation surface), so an invisible credential prompt would pin an open HTTP request until the timeout. `gitNonInteractiveEnv()` closes all four prompt paths at once: `GIT_TERMINAL_PROMPT=0`, empty `GIT_ASKPASS`/`SSH_ASKPASS` + `SSH_ASKPASS_REQUIRE=never` + empty `DISPLAY`, `GCM_INTERACTIVE=never`, and `ssh -oBatchMode=yes`. `HOME`/`PATH` are inherited on purpose — a user whose own agent or credential helper already works keeps working (so a private repo may well clone; Codeman just never collects or stores credentials, and refuses a `user:password@` URL).
+- ⚠️ **Bounded in time, output and concurrency.** Timeout → SIGTERM → SIGKILL, signalled to the whole process GROUP (`detached: true`, negative pid) because `git clone` fans out into `git-remote-https`/`index-pack` children that a polite signal to the parent leaves running. stderr is kept as a bounded, credential-redacted, control-stripped TAIL; `ls-remote` stdout is capped and refs are capped at 500 each. A small global pool (default 2, `CODEMAN_MAX_GIT_OPERATIONS`) caps concurrent git network ops, same reasoning as `document-conversion-limiter.ts`.
+- **Repository contents beat scaffolding.** An existing `CLAUDE.md` is kept (a generated one is written only when absent) and hooks are MERGED into whatever `.claude/settings.local.json` the repo shipped. A repo that ships its own `.claude/settings*.json` is reported back as a warning, because repo-supplied hooks run on the user's machine as soon as a session starts there.
+- **Failure leaves nothing behind.** The destination is removed only when it did not exist before the attempt, and a pre-existing directory is refused rather than cloned into, so a failed clone never squats on a case name and never touches an existing tree.
+- ⚠️ **Error detail comes from the LAST diagnostic line, not the first.** `git clone` opens with `Cloning into '<dest>'…`, so a first-line pick reported the destination path as the reason a bad branch failed (observed against a real remote). `NOT_FOUND` wording must also say "or private": GitHub answers "Repository not found" for a private repo and a typo alike when unauthenticated.
+- **Multi-user**: NOT admin-gated, unlike `/api/cases/link` — it writes only inside the caller's own `resolveCasesDir`. The exception is a `local`-transport source (an absolute path or `file://`), which is admin-only there because per-user spaces live inside one `$HOME` and a local clone would read straight through that boundary.
+- **UI** (`case-clone` tab in the Add Case modal): debounced preflight paints a verdict under the field, fills the case name from the parsed repo (until the user types their own), and turns the branch/tag field into a datalist of the remote's real refs. The **Brain** picker sets the toolbar run mode on success (gated by `isCliAvailable()`, like `#runModeMenu`), so Run already points at the chosen CLI; starting a session stays opt-in. The tab hides itself when the server reports no `git` (injected via `window.__codemanCliAvailable`).
+
+Tests: `test/git-clone.test.ts` (pure half exhaustively, plus REAL git against a REAL local bare repo for clone/ref/timeout/cleanup), `test/routes/case-clone-routes.test.ts` (deliberately **unmocked fs**, real clone through the endpoint).
+
 ### 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`.