fix: improve state detection accuracy and notification UX

- Hook reads JSON from stdin (not env vars) matching Claude Code protocol
- end_turn = Idle (not NeedsInput); real questions come from hooks
- Permission prompt (stale tool_use) never becomes Idle
- Notifications auto-expire after 10s (--expire-time)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

main.go

@@ -149,7 +149,7 @@ func main() {
 		runI3Bar(sockPath)
 
 	case "hook":
-		event := parseHookEnv()
+		event := parseHookStdin()
 		if event.HookEventName == "" {
 			os.Exit(0)
 		}