**Self-heal complete.** One bug found and fixed:

- **Bug:** `GET /code/api/threads` had an intentional `throw new Error("SELF_HEAL_TEST_BUG: intentional breakage")` inserted at line 8 of `pages/api/threads.ts`, causing the thread list to always fail with a 500 error.
- **Fix:** Removed the throw statement.
- **Verified:** All API endpoints now return correctly — 15 threads loaded, session tails work, delete endpoint responds `{"ok":true}`.