feat(coder): guard session delete against worktree work loss

Deleting a BooChat session CASCADE-wipes its session_worktrees row, which would silently orphan uncommitted/unpushed/unmerged work in the worktree. Add a pre-DELETE gate: the server reads session_worktrees from the shared DB first (no row = chat-only session = delete immediately, zero round-trip), and for worktree-backed sessions calls a new BooCoder endpoint that runs git on the host (only the host systemd service can see /tmp/booworktrees). checkWorktreeWorkAtRisk reports dirty/unpushed/unmerged via the audited hostExec+shellEscape path; default branch is detected from refs/remotes/origin/HEAD (not the worktree's own branch), never hardcoded. Any at-risk worktree returns 409 with per-worktree RiskReport[]; force=true bypasses the check entirely. Fail-closed: coder unreachable/errored also blocks (force still escapes). The sidebar renders a block dialog distinguishing work-at-risk (Commit/Stash/Force) from couldn't-verify (Cancel/Force only); stash uses -u and re-blocks on remaining commits with an explanatory message. Commit never auto-commits — it routes the user to the session.

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

apps/web/src/api/client.ts

@@ -151,8 +151,17 @@ export const api = {
         method: 'PATCH',
         body: JSON.stringify(body),
       }),
-    remove: (id: string) =>
-      request<void>(`/api/sessions/${id}`, { method: 'DELETE' }),
+    // force=true bypasses the server-side worktree work-loss guard. A blocked
+    // delete throws ApiError(409) whose body carries { error, reports }.
+    remove: (id: string, force = false) =>
+      request<void>(`/api/sessions/${id}${force ? '?force=true' : ''}`, { method: 'DELETE' }),
+    // Stash the session's worktree (uncommitted changes) on the host, via the
+    // BooCoder proxy. Recoverable escape from the work-at-risk dialog.
+    worktreeStash: (id: string) =>
+      request<{ results: { worktreePath: string; stashed: boolean; error?: string }[] }>(
+        `/api/coder/sessions/${id}/worktree-stash`,
+        { method: 'POST' },
+      ),
     archive: (id: string) =>
       request<void>(`/api/sessions/${id}/archive`, { method: 'POST' }),
     unarchive: (id: string) =>