fix: remove observable states from agent_state (discover, don't track)

The agent_state field was recording observable state like "running",
"dead", "idle" which violated the "Discover, Don't Track" principle.
This caused stale state bugs where agents were marked "dead" in beads
but actually running in tmux.

Changes:
- Remove daemon's checkStaleAgents() which marked agents "dead"
- Simplify ensureXxxRunning() to use tmux.IsClaudeRunning() directly
- Remove reportAgentState() calls from gt prime and gt handoff
- Add SetHookBead/ClearHookBead helpers that don't update agent_state
- Use ClearHookBead in gt done and gt unsling
- Simplify gt status to derive state from tmux, not bead

Non-observable states (stuck, awaiting-gate, muted, paused) are still
set because they represent intentional agent decisions that can't be
discovered from tmux state.

Fixes: gt-zecmc

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

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

internal/cmd/done.go

@@ -356,12 +356,10 @@ func runDone(cmd *cobra.Command, args []string) error {
 	return nil
 }
 
-// updateAgentStateOnDone updates the agent bead state when work is complete.
-// Maps exit type to agent state:
-//   - COMPLETED → "done"
-//   - ESCALATED → "stuck"
-//   - DEFERRED → "idle"
-//   - PHASE_COMPLETE → "awaiting-gate"
+// updateAgentStateOnDone clears the agent's hook and reports cleanup status.
+// Per gt-zecmc: observable states ("done", "idle") removed - use tmux to discover.
+// Non-observable states ("stuck", "awaiting-gate") are still set since they represent
+// intentional agent decisions that can't be observed from tmux.
 //
 // Also self-reports cleanup_status for ZFC compliance (#10).
 func updateAgentStateOnDone(cwd, townRoot, exitType, _ string) { // issueID unused but kept for future audit logging
@@ -384,22 +382,6 @@ func updateAgentStateOnDone(cwd, townRoot, exitType, _ string) { // issueID unus
 		return
 	}
 
-	// Map exit type to agent state
-	var newState string
-	switch exitType {
-	case ExitCompleted:
-		newState = "done"
-	case ExitEscalated:
-		newState = "stuck"
-	case ExitDeferred:
-		newState = "idle"
-	case ExitPhaseComplete:
-		newState = "awaiting-gate"
-	default:
-		return
-	}
-
-	// Update agent bead with new state and clear hook_bead (work is done)
 	// Use rig path for slot commands - bd slot doesn't route from town root
 	var beadsPath string
 	switch ctx.Role {
@@ -423,11 +405,26 @@ func updateAgentStateOnDone(cwd, townRoot, exitType, _ string) { // issueID unus
 		}
 	}
 
-	emptyHook := ""
-	if err := bd.UpdateAgentState(agentBeadID, newState, &emptyHook); err != nil {
-		// Log warning instead of silent ignore - helps debug cross-beads issues
-		fmt.Fprintf(os.Stderr, "Warning: couldn't update agent %s state on done: %v\n", agentBeadID, err)
-		return
+	// Clear the hook (work is done) - gt-zecmc
+	if err := bd.ClearHookBead(agentBeadID); err != nil {
+		fmt.Fprintf(os.Stderr, "Warning: couldn't clear agent %s hook: %v\n", agentBeadID, err)
+	}
+
+	// Only set non-observable states - "stuck" and "awaiting-gate" are intentional
+	// agent decisions that can't be discovered from tmux. Skip "done" and "idle"
+	// since those are observable (no session = done, session + no hook = idle).
+	switch exitType {
+	case ExitEscalated:
+		// "stuck" = agent is requesting help - not observable from tmux
+		if _, err := bd.Run("agent", "state", agentBeadID, "stuck"); err != nil {
+			fmt.Fprintf(os.Stderr, "Warning: couldn't set agent %s to stuck: %v\n", agentBeadID, err)
+		}
+	case ExitPhaseComplete:
+		// "awaiting-gate" = agent is waiting for external trigger - not observable
+		if _, err := bd.Run("agent", "state", agentBeadID, "awaiting-gate"); err != nil {
+			fmt.Fprintf(os.Stderr, "Warning: couldn't set agent %s to awaiting-gate: %v\n", agentBeadID, err)
+		}
+	// ExitCompleted and ExitDeferred don't set state - observable from tmux
 	}
 
 	// ZFC #10: Self-report cleanup status