chengyongru 15c2bd25b3 refactor(heartbeat): remove Completed section and tighten section gating
- Remove ## Completed section from HEARTBEAT.md template; completed
  tasks should be deleted, not accumulated
- Change in_active_section from tri-state (None/True/False) to bool
  (True/False) so stray text before any ## heading no longer triggers
  heartbeat
- Add test cases for stray pre-heading text and ## Notes section
- Update docs/chat-commands.md to reference ## Active Tasks
2026-05-31 15:15:37 +08:00
..