fix: resolve /clear command and ESC key lag caused by hooks system

- Make hook events fire-and-forget in clearCommand to avoid blocking UI
- Move context.ui.clear() before resetChat for immediate responsiveness
- Add hasHooksForEvent() fast-path check to HookSystem and Config
- Skip MessageBus round-trips in client.ts when no hooks are registered
- Add comprehensive unit tests for all changes

Fixes #2651

packages/core/src/config/config.test.ts

@@ -1582,4 +1582,37 @@ describe('Model Switching and Config Updates', () => {
     const updatedConfig = config.getContentGeneratorConfig();
     expect(updatedConfig['contextWindowSize']).toBe(128_000);
   });
+
+  describe('hasHooksForEvent', () => {
+    it('should return false when hookSystem is not initialized', () => {
+      const config = new Config(baseParams);
+      expect(config.hasHooksForEvent('Stop')).toBe(false);
+    });
+
+    it('should delegate to hookSystem.hasHooksForEvent when hookSystem exists', () => {
+      const config = new Config(baseParams);
+      const mockHasHooksForEvent = vi.fn().mockReturnValue(true);
+      const mockHookSystem = {
+        hasHooksForEvent: mockHasHooksForEvent,
+      };
+      // @ts-expect-error - accessing private for testing
+      config['hookSystem'] = mockHookSystem;
+
+      expect(config.hasHooksForEvent('UserPromptSubmit')).toBe(true);
+      expect(mockHasHooksForEvent).toHaveBeenCalledWith('UserPromptSubmit');
+    });
+
+    it('should return false when hookSystem has no hooks for the event', () => {
+      const config = new Config(baseParams);
+      const mockHasHooksForEvent = vi.fn().mockReturnValue(false);
+      const mockHookSystem = {
+        hasHooksForEvent: mockHasHooksForEvent,
+      };
+      // @ts-expect-error - accessing private for testing
+      config['hookSystem'] = mockHookSystem;
+
+      expect(config.hasHooksForEvent('Stop')).toBe(false);
+      expect(mockHasHooksForEvent).toHaveBeenCalledWith('Stop');
+    });
+  });
 });

packages/core/src/config/config.ts

@@ -1769,6 +1769,15 @@ export class Config {
     return this.hookSystem;
   }
 
+  /**
+   * Fast-path check: returns true only when hooks are enabled AND there are
+   * registered hooks for the given event name.  Callers can use this to skip
+   * expensive MessageBus round-trips when no hooks are configured.
+   */
+  hasHooksForEvent(eventName: string): boolean {
+    return this.hookSystem?.hasHooksForEvent(eventName) ?? false;
+  }
+
   /**
    * Check if hooks are enabled.
    */