fix: Clear polecat hook on completion by using rig path (gt-2wc1n)

The bd slot command doesn't route correctly from town root - it only
works when run from the rig directory. This fix changes done.go to
use the rig path (filepath.Join(townRoot, ctx.Rig)) instead of
townRoot when calling slot commands.

Bug: gt polecat nuke was blocked by stale hooks on closed beads
because gt done wasn't actually clearing the hook_bead field.

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

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

internal/cmd/done.go

@@ -393,8 +393,15 @@ func updateAgentStateOnDone(cwd, townRoot, exitType, _ string) { // issueID unus
 	}
 
 	// Update agent bead with new state and clear hook_bead (work is done)
-	// Use town root for routing - ensures cross-beads references work
-	bd := beads.New(townRoot)
+	// Use rig path for slot commands - bd slot doesn't route from town root
+	var beadsPath string
+	switch ctx.Role {
+	case RoleMayor, RoleDeacon:
+		beadsPath = townRoot
+	default:
+		beadsPath = filepath.Join(townRoot, ctx.Rig)
+	}
+	bd := beads.New(beadsPath)
 	emptyHook := ""
 	if err := bd.UpdateAgentState(agentBeadID, newState, &emptyHook); err != nil {
 		// Log warning instead of silent ignore - helps debug cross-beads issues