feat: add hook-based idle detection for respawn controller

Implement multi-phase improvement to respawn controller's idle detection:

Phase 1 - Stop Hook Detection:
- Add signalStopHook() method - definitive signal when Claude finishes
- 3s confirmation timer to handle race conditions
- Skip AI check when hook received (100% confidence)

Phase 2 - idle_prompt Detection:
- Add signalIdlePrompt() method - fires after 60s+ of idle
- Immediately confirms idle (no confirmation timer needed)

Phase 3 - Transcript File Monitoring:
- New TranscriptWatcher class watches session JSONL files
- Detects: completion, tool execution, plan mode, errors
- Signals respawn controller for supporting detection

Web UI Updates:
- Hook indicator with purple styling and pulse animation
- Shows "Stop hook received" or "idle_prompt hook received"
- 100% confidence displayed with hook-confirmed style

This significantly improves idle detection reliability by using
definitive signals from Claude Code rather than parsing terminal output.

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

src/web/public/app.js

@@ -2153,6 +2153,19 @@ class ClaudemanApp {
     const waitingEl = this.$('detectionWaiting');
     const confidenceEl = this.$('detectionConfidence');
     const aiCheckEl = document.getElementById('detectionAiCheck');
+    const hookEl = document.getElementById('detectionHook');
+
+    // Hook-based detection indicator (highest priority signals)
+    if (hookEl) {
+      if (detection.stopHookReceived || detection.idlePromptReceived) {
+        const hookType = detection.idlePromptReceived ? 'idle_prompt' : 'Stop';
+        hookEl.textContent = `🎯 ${hookType} hook received`;
+        hookEl.className = 'detection-hook hook-active';
+        hookEl.style.display = '';
+      } else {
+        hookEl.style.display = 'none';
+      }
+    }
 
     // Simplified status - only show when meaningful
     if (detection.statusText && detection.statusText !== 'Watching...') {
@@ -2171,8 +2184,14 @@ class ClaudemanApp {
       confidenceEl.textContent = `${confidence}%`;
       confidenceEl.style.display = '';
       confidenceEl.className = 'detection-confidence';
-      if (confidence >= 60) confidenceEl.classList.add('high');
-      else if (confidence >= 30) confidenceEl.classList.add('medium');
+      // Hook signals give 100% confidence
+      if (detection.stopHookReceived || detection.idlePromptReceived) {
+        confidenceEl.classList.add('hook-confirmed');
+      } else if (confidence >= 60) {
+        confidenceEl.classList.add('high');
+      } else if (confidence >= 30) {
+        confidenceEl.classList.add('medium');
+      }
     } else {
       confidenceEl.style.display = 'none';
     }

src/web/public/index.html

@@ -73,6 +73,7 @@
         <span class="detection-status" id="detectionStatus"></span>
         <span class="detection-waiting" id="detectionWaiting" style="display: none;"></span>
         <span class="detection-confidence" id="detectionConfidence"></span>
+        <span class="detection-hook" id="detectionHook" style="display: none;"></span>
         <span class="detection-ai-check" id="detectionAiCheck" style="display: none;"></span>
         <span class="respawn-spacer"></span>
         <span class="respawn-cycles">#<span id="respawnCycleCount">0</span></span>

src/web/public/styles.css

@@ -671,6 +671,31 @@ body {
   color: var(--yellow);
 }
 
+.detection-confidence.hook-confirmed {
+  background: rgba(139, 92, 246, 0.3);
+  color: var(--purple, #a78bfa);
+}
+
+.detection-hook {
+  font-size: 0.7rem;
+  padding: 0.1rem 0.4rem;
+  border-radius: 3px;
+  background: rgba(139, 92, 246, 0.15);
+  color: var(--purple, #a78bfa);
+}
+
+.detection-hook.hook-active {
+  background: rgba(139, 92, 246, 0.25);
+  color: var(--purple, #a78bfa);
+  font-weight: 500;
+  animation: pulse-hook 1.5s ease-in-out infinite;
+}
+
+@keyframes pulse-hook {
+  0%, 100% { opacity: 1; }
+  50% { opacity: 0.7; }
+}
+
 @keyframes spin {
   to { transform: rotate(360deg); }
 }