Palace Code self-heal complete — **everything passed**.

**Test summary:**
- HTTP 200, page renders correctly
- All 9 API endpoints working (threads, session-tails, linear-issues, attach-thread, update-thread, delete-thread)
- 5 threads found in the last 24h window, 1 in the 1h window
- Layout elements present: title, split-panel, time window selector, new chat button, nav, Butler overlay
- No console errors, no broken logic in any source file

One non-breaking observation: the `threads` API response omits the `heartbeats` field that the TypeScript type declares as required — but `use-threads.ts` already handles this with `data.heartbeats || {}`, and `heartbeats` is never rendered in the UI anyway. No fix needed.