refactor(hooks): split session-notification and unstable-agent-babysitter

Extract notification and babysitter logic:
- session-notification-formatting.ts, session-notification-scheduler.ts
- session-notification-sender.ts, session-todo-status.ts
- task-message-analyzer.ts: message analysis for babysitter hook

src/hooks/unstable-agent-babysitter/index.ts

@@ -1 +1,9 @@
 export { createUnstableAgentBabysitterHook } from "./unstable-agent-babysitter-hook"
+export {
+  buildReminder,
+  extractMessages,
+  getMessageInfo,
+  getMessageParts,
+  isUnstableTask,
+  THINKING_SUMMARY_MAX_CHARS,
+} from "./task-message-analyzer"