feat(04-02): add agent lifecycle events to events module

- AgentSpawnedEvent for new agent creation
- AgentStoppedEvent with reason (user_requested, task_complete, error, waiting_for_input)
- AgentCrashedEvent for unexpected failures
- AgentResumedEvent for session resumption
- AgentWaitingEvent when agent pauses on AskUserQuestion
- Updated DomainEventMap union with all agent events

src/events/index.ts

@@ -20,6 +20,11 @@ export type {
   WorktreeRemovedEvent,
   WorktreeMergedEvent,
   WorktreeConflictEvent,
+  AgentSpawnedEvent,
+  AgentStoppedEvent,
+  AgentCrashedEvent,
+  AgentResumedEvent,
+  AgentWaitingEvent,
   DomainEventMap,
   DomainEventType,
 } from './types.js';