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/coder/src/routes/worktree-safety.ts

@@ -0,0 +1,45 @@
+/**
+ * Session-delete work-loss guard (coder side).
+ *
+ * Session delete itself lives in apps/server (Docker), which CANNOT see the
+ * host worktree dirs (/tmp/booworktrees) or run git on them. Only BooCoder
+ * (host systemd) can. So the server's DELETE route calls these endpoints
+ * pre-delete to learn whether a session's worktree holds work at risk, and to
+ * stash it. The server owns the gate; coder owns the git truth.
+ */
+import type { FastifyInstance } from 'fastify';
+import type { Sql } from '../db.js';
+import { checkWorktreeWorkAtRisk, stashWorktree } from '../services/worktrees.js';
+
+export function registerWorktreeSafetyRoutes(app: FastifyInstance, sql: Sql): void {
+  // GET risk for a session's worktree(s). One row per session today (PK on
+  // session_id); the loop already handles the Phase-1.5 multi-worktree case.
+  app.get<{ Params: { sessionId: string } }>(
+    '/api/sessions/:sessionId/worktree-risk',
+    async (req) => {
+      const rows = await sql<{ worktree_path: string }[]>`
+        SELECT worktree_path FROM session_worktrees WHERE session_id = ${req.params.sessionId}
+      `;
+      const reports = [];
+      for (const row of rows) {
+        reports.push(await checkWorktreeWorkAtRisk(row.worktree_path));
+      }
+      return { reports };
+    },
+  );
+
+  // Stash a session's worktree(s) — clears the dirty risk; recoverable.
+  app.post<{ Params: { sessionId: string } }>(
+    '/api/sessions/:sessionId/worktree-stash',
+    async (req) => {
+      const rows = await sql<{ worktree_path: string }[]>`
+        SELECT worktree_path FROM session_worktrees WHERE session_id = ${req.params.sessionId}
+      `;
+      const results = [];
+      for (const row of rows) {
+        results.push({ worktreePath: row.worktree_path, ...(await stashWorktree(row.worktree_path)) });
+      }
+      return { results };
+    },
+  );
+}