feat(deacon): add stale hooked bead cleanup (gt-2yls3)

Add `gt deacon stale-hooks` command to find and unhook stale beads.

Problem: Beads can get stuck in 'hooked' status when agents die or
abandon work without properly unhooking.

Solution:
- New command scans for hooked beads older than threshold (default 1h)
- Checks if assignee agent is still alive (tmux session exists)
- Unhooks beads with dead agents (sets status back to 'open')
- Supports --dry-run to preview without making changes

Also adds "stale-hook-check" step to Deacon patrol formula.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/formula/formulas/mol-deacon-patrol.formula.toml

@@ -340,10 +340,43 @@ gt mail send mayor/ -s "Health: <rig> <component> unresponsive" \\
 
 Reset unresponsive_cycles to 0 when component responds normally."""
 
+[[steps]]
+id = "stale-hook-check"
+title = "Cleanup stale hooked beads"
+needs = ["health-scan"]
+description = """
+Find and unhook beads stuck in 'hooked' status.
+
+Beads can get stuck in 'hooked' status when agents die or abandon work without
+properly unhooking. This step cleans them up so the work can be reassigned.
+
+**Step 1: Preview stale hooks**
+```bash
+gt deacon stale-hooks --dry-run
+```
+
+Review the output - it shows:
+- Hooked beads older than 1 hour
+- Whether the assignee agent is still alive
+- What action would be taken
+
+**Step 2: If stale hooks found with dead agents, unhook them**
+```bash
+gt deacon stale-hooks
+```
+
+This sets status back to 'open' for beads whose assignee agent is no longer running.
+
+**Step 3: If no stale hooks**
+No action needed - hooks are healthy.
+
+**Note**: This is a backstop. Primary fix is ensuring agents properly unhook
+beads when they exit or hand off work."""
+
 [[steps]]
 id = "zombie-scan"
 title = "Backup check for zombie polecats"
-needs = ["health-scan"]
+needs = ["stale-hook-check"]
 description = """
 Defense-in-depth check for zombie polecats that Witness should have cleaned.