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/index.ts

@@ -1,6 +1,10 @@
 export { createTodoContinuationEnforcer, type TodoContinuationEnforcer } from "./todo-continuation-enforcer";
 export { createContextWindowMonitorHook } from "./context-window-monitor";
 export { createSessionNotification } from "./session-notification";
+export { sendSessionNotification, playSessionNotificationSound, detectPlatform, getDefaultSoundPath } from "./session-notification-sender";
+export { buildWindowsToastScript, escapeAppleScriptText, escapePowerShellSingleQuotedText } from "./session-notification-formatting";
+export { hasIncompleteTodos } from "./session-todo-status";
+export { createIdleNotificationScheduler } from "./session-notification-scheduler";
 export { createSessionRecoveryHook, type SessionRecoveryHook, type SessionRecoveryOptions } from "./session-recovery";
 export { createCommentCheckerHooks } from "./comment-checker";
 export { createToolOutputTruncatorHook } from "./tool-output-truncator";