test(agent): add MockAgentManager mode tests

- Test default execute mode on spawn
- Test discuss mode with context_complete scenario
- Test breakdown mode with breakdown_complete scenario
- Verify stopped event reasons for each mode

src/agent/mock-manager.test.ts

@@ -595,6 +595,98 @@ describe('MockAgentManager', () => {
     });
   });
 
+  // ===========================================================================
+  // Agent modes (execute, discuss, breakdown)
+  // ===========================================================================
+
+  describe('agent modes', () => {
+    it('should spawn agent with default execute mode', async () => {
+      const agent = await manager.spawn({
+        name: 'exec-agent',
+        taskId: 't1',
+        prompt: 'test',
+      });
+      expect(agent.mode).toBe('execute');
+    });
+
+    it('should spawn agent in discuss mode', async () => {
+      manager.setScenario('discuss-agent', {
+        status: 'context_complete',
+        delay: 0,
+        decisions: [{ topic: 'Auth', decision: 'JWT', reason: 'Standard' }],
+        summary: 'Auth discussion complete',
+      });
+
+      const agent = await manager.spawn({
+        name: 'discuss-agent',
+        taskId: 't1',
+        prompt: 'discuss auth',
+        mode: 'discuss',
+      });
+
+      expect(agent.mode).toBe('discuss');
+    });
+
+    it('should spawn agent in breakdown mode', async () => {
+      manager.setScenario('breakdown-agent', {
+        status: 'breakdown_complete',
+        delay: 0,
+        phases: [
+          { number: 1, name: 'Foundation', description: 'Core setup' },
+          { number: 2, name: 'Features', description: 'Main features' },
+        ],
+      });
+
+      const agent = await manager.spawn({
+        name: 'breakdown-agent',
+        taskId: 't1',
+        prompt: 'breakdown work',
+        mode: 'breakdown',
+      });
+
+      expect(agent.mode).toBe('breakdown');
+    });
+
+    it('should emit stopped event with context_complete reason', async () => {
+      manager.setScenario('discuss-done', {
+        status: 'context_complete',
+        delay: 0,
+        decisions: [],
+        summary: 'Done',
+      });
+
+      await manager.spawn({
+        name: 'discuss-done',
+        taskId: 't1',
+        prompt: 'test',
+        mode: 'discuss',
+      });
+      await vi.runAllTimersAsync();
+
+      const stopped = eventBus.emittedEvents.find((e) => e.type === 'agent:stopped');
+      expect(stopped?.payload.reason).toBe('context_complete');
+    });
+
+    it('should emit stopped event with breakdown_complete reason', async () => {
+      manager.setScenario('breakdown-done', {
+        status: 'breakdown_complete',
+        delay: 0,
+        phases: [],
+      });
+
+      await manager.spawn({
+        name: 'breakdown-done',
+        taskId: 't1',
+        prompt: 'test',
+        mode: 'breakdown',
+      });
+      await vi.runAllTimersAsync();
+
+      const stopped = eventBus.emittedEvents.find((e) => e.type === 'agent:stopped');
+      expect(stopped?.payload.reason).toBe('breakdown_complete');
+    });
+  });
+
   // ===========================================================================
   // Structured question data (new schema tests)
   // ===========================================================================