Make Thread Organizer use pinned threads as an inbox

[brsbl]

Summary

Turn Thread Organizer into an inbox workflow:

• pin idle and failed threads into the top inbox area
• unpin every active thread, regardless of who created the pin
• preserve each thread’s semantic section throughout its lifecycle
• adopt existing visible root threads on startup
• default to apply mode while retaining observe mode

Root cause

The prior plugin only tracked threads created while it was loaded and defaulted to observe mode. Most existing threads therefore had no organizer state and received no lifecycle updates.

Startup reconciliation now snapshots the thread list, refreshes each thread before adoption, and runs as a host-managed background service so reloads cannot overlap plugin instances.

A follow-up live regression showed that ownership tracking incorrectly preserved manually pinned active threads. Pinning is now reserved for Inbox state, so active work is always unpinned.

Validation

• npm run check --workspace bb-plugin-thread-organizer
  • typecheck passed
  • production build passed
  • 62 tests passed
• npm run hygiene passed
• installed source rebuilt and reloaded successfully
• live active-thread reproduction is now unpinned

The repository-wide artifact command reaches Thread Organizer successfully but remains blocked by the existing missing plugins/timeline-comments/dist/server.js artifact.