refactor: hybrid indicator+timeout detection in respawn controller

- Primary: Use '↵ send' indicator for immediate response when ready
- Fallback: Use timeout-based detection for prompt patterns
- Add working indicators: Synthesizing, Brewing, ✻, ✽
- Cleaner step completion handlers (checkUpdateComplete, etc.)

The hybrid approach responds immediately when Claude shows the
suggestion indicator, while still having timeout fallback for
reliability.

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

test/respawn-controller.test.ts

@@ -26,25 +26,31 @@ class MockSession extends EventEmitter {
     this.emit('terminal', data);
   }
 
-  // Simulate prompt appearing
+  // Simulate prompt appearing (basic prompt character)
   simulatePrompt(): void {
     this.emit('terminal', '❯ ');
   }
 
+  // Simulate ready state with the definitive indicator
+  simulateReady(): void {
+    this.emit('terminal', '↵ send');
+  }
+
   // Simulate working state
   simulateWorking(): void {
     this.emit('terminal', 'Thinking... ⠋');
   }
 
-  // Simulate clear completion
+  // Simulate clear completion (followed by ready indicator)
   simulateClearComplete(): void {
     this.emit('terminal', 'conversation cleared');
+    setTimeout(() => this.simulateReady(), 50);
   }
 
-  // Simulate init completion
+  // Simulate init completion (followed by ready indicator)
   simulateInitComplete(): void {
     this.emit('terminal', 'Analyzing CLAUDE.md...');
-    setTimeout(() => this.simulatePrompt(), 100);
+    setTimeout(() => this.simulateReady(), 100);
   }
 }