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>

CLAUDE.md

@@ -43,7 +43,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 2. **Frontend changes**: Use Playwright to load the page and assert the UI renders correctly. Use `waitUntil: 'domcontentloaded'` (not `networkidle` — SSE keeps the connection open). Wait 3-4s for polling/async data to populate, then check element visibility, text content, and CSS values
 3. **Only after verification passes**, proceed with COM
 
-The production server caches static files for 1 year, `immutable` (`maxAge: '1y'` in `server.ts`). To avoid stale frontend after a deploy, `renderIndexHtml` runs `cacheBustAssets(html)` — it appends `?v=<mtime>` to **every same-origin `.js`/`.css`** reference (mtime memoized ~1s so a burst of renders is cheap; external/already-versioned/missing refs untouched). Because `index.html` is served `no-cache`, a **normal reload now picks up edited modules/styles — no hard refresh needed** (the gesture bundle is injected separately with its own `?v=`). If you add an asset referenced by an _absolute_ URL or from JS rather than a `<script>/<link>` tag, it won't be auto-busted.
+The production server caches static files for 1 year, `immutable` (`maxAge: '1y'` in `server.ts`). To avoid stale frontend after a deploy, `renderIndexHtml` runs `cacheBustAssets(html)` — it appends `?v=<mtime>` to **every same-origin `.js`/`.css`** reference (mtime memoized ~1s so a burst of renders is cheap; external/already-versioned/missing refs untouched). Because `index.html` is served `no-cache`, a **normal reload now picks up edited modules/styles — no hard refresh needed** (the gesture bundle is injected separately with its own `?v=`). If you add an asset referenced by an _absolute_ URL or from JS rather than a `<script>/<link>` tag, it won't be auto-busted. ⚠️ **`index.html` itself is the exception: it is read ONCE into `indexHtmlTemplate` in the `WebServer` constructor**, so editing markup in dev needs a server restart (edited `.js`/`.css` do not) — otherwise you debug a "CSS class that doesn't apply" that is really an element still missing from the served HTML.
 
 ## COM Shorthand (Deployment)
 
@@ -226,6 +226,8 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 
 **Ultracode / workflow-run visualization** (opt-in, default OFF): the Workflow tool writes a completion artifact only at run *end*, so live in-flight runs exist solely as transcript dirs. `workflow-run-watcher.ts` therefore synthesizes ACTIVE runs from transcripts until the completion artifact appears and supersedes them. It is **STANDALONE** and deliberately never imports or touches `subagent-watcher.ts`, despite reading the same tree. Two independent toggles: `showUltracodeAgents` (docked panel) and `ultracodeFloatingWindows` (floating windows); the watcher starts if **either** is on. → [architecture-invariants#ultracode--workflow-run-visualization](docs/architecture-invariants.md#ultracode-and-workflow-run-visualization)
 
+**Clone a repository as a case** (issue #236, Add Case → **Clone Repo**): `POST /api/cases/clone` clones a public repo into the caller's case space synchronously (request held open, bounded by `GIT_CLONE_TIMEOUT_MS`, no job store); `POST /api/cases/clone-preflight` reports whether the URL can be cloned anonymously plus its real branches/tags. Core in `src/git-clone.ts`. ⚠️ **The URL is a code-execution surface**: `ext::sh -c <cmd>` (and ANY `<name>::<payload>` helper) makes git run a command, so every `::` form is refused, a leading `-` is refused, and every spawn is an argv array with `--` before the operands. ⚠️ **Non-interactive or the open request hangs** — `gitNonInteractiveEnv()` closes the terminal/askpass/ssh/GCM prompt paths; `HOME`/`PATH` stay inherited, so a user's OWN credential helper may authenticate (Codeman still never collects or stores credentials, and refuses a `user:password@` URL). ⚠️ Timeout kills the process GROUP (clone fans out into child processes), the destination is removed only if this attempt created it, and repository contents win over scaffolding (existing `CLAUDE.md` kept, hooks merged, repo-shipped `.claude/settings*` reported as a warning since its hooks run locally). The **Brain** picker sets the toolbar run mode on success. → [architecture-invariants#clone-a-repository-as-a-case](docs/architecture-invariants.md#clone-a-repository-as-a-case)
+
 **Cross-session search**: `GET /api/search` federates an in-memory search over session metadata, run-summary events, and attachment-history entries. The pure core `searchSources()` does substring matching with hard per-type caps: **no regex (so no ReDoS) and no filesystem reads (so no traversal)**. The server-private `externalPath` is never read. → [architecture-invariants#cross-session-search](docs/architecture-invariants.md#cross-session-search)
 
 **Web tabs** (dashboard URLs as tabs): a saved URL renders as a tab beside agent sessions. **NOT a sixth `SessionMode`** (no PTY, no tmux, no respawn), same reasoning that keeps Docker/remote-SSH as case overlays. Dashboards are **proxied through Codeman's own origin** by default, because a direct iframe fails three ways at once: prod is HTTPS so `http://` targets are blocked as mixed content, many dashboards send `X-Frame-Options: DENY`, and our own `default-src 'self'` CSP blocks cross-origin frames. Proxying leaves the prod CSP unchanged (`/webview/...` is `'self'`). ⚠️ The proxy is **NOT an API surface**: it authenticates on an in-memory capability in the path and is correspondingly exempt from the cookie + Origin checks; that exemption is fenced to safe methods and non-`/api` paths and is pinned by `test/webview-auth-exemption.test.ts`. ⚠️ Iframes omit `allow-same-origin` unless a dashboard is explicitly marked `trusted`, and `Authorization`/`codeman_session` are stripped upstream in **both** modes so `CODEMAN_PASSWORD` cannot leak. ⚠️ A sandboxed frame is **opaque-origin**, which breaks two things `curl` can never reproduce: its runtime-built root-absolute URLs escape `<base>` (fixed by an injected `runtimeUrlShim()`), and its same-host `fetch`/XHR are CORS-checked with `Origin: null` (fixed by `buildProxyCorsHeaders()` plus exempting the proxy from the global `OPTIONS`-204 short-circuit in `registerSecurityHeaders`). Both present as the dashboard's own "Failed to fetch" while the page renders fine. → [architecture-invariants#web-tabs](docs/architecture-invariants.md#web-tabs), `docs/web-tabs.md`
@@ -298,7 +300,7 @@ Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. L
 
 ### API Routes
 
-~200 handlers across 21 route files in `src/web/routes/`: system (45), sessions (34), cases (27), files (16), orchestrator (10), ralph (9), cron (9), admin (8), plan (8), respawn (7), webviews (6 + the `/webview/:cap/*` proxy), mux (5), push (4), scheduled (4, legacy `ScheduledRun`), me (2), teams (2), search (1), hooks (1), clipboard (1), status-telemetry (1), ws (1 WebSocket). Each file has `@fileoverview` with endpoint details.
+~200 handlers across 21 route files in `src/web/routes/`: system (45), sessions (34), cases (29), files (16), orchestrator (10), ralph (9), cron (9), admin (8), plan (8), respawn (7), webviews (6 + the `/webview/:cap/*` proxy), mux (5), push (4), scheduled (4, legacy `ScheduledRun`), me (2), teams (2), search (1), hooks (1), clipboard (1), status-telemetry (1), ws (1 WebSocket). Each file has `@fileoverview` with endpoint details.
 
 **HTTP contract** (stable since 0.9.x, see `docs/versioning-policy.md`; full envelope/status/error-code/SSE spec in `docs/api-reference.md`): responses use the `ApiResponse<T>` envelope — `{ success: true, data? }` or `{ success: false, error, errorCode }` (`src/types/api.ts`). `/api/v1/*` is a versioned alias of `/api/*` (URL rewrite in `server.ts`).