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>

setup.go

@@ -7,15 +7,11 @@ import (
 	"path/filepath"
 )
 
-// parseHookEnv builds a HookEvent from Claude Code hook environment variables.
-func parseHookEnv() HookEvent {
-	return HookEvent{
-		SessionID:        os.Getenv("SESSION_ID"),
-		Cwd:              os.Getenv("SESSION_CWD"),
-		HookEventName:    os.Getenv("HOOK_EVENT_NAME"),
-		NotificationType: os.Getenv("NOTIFICATION_TYPE"),
-		ToolName:         os.Getenv("TOOL_NAME"),
-	}
+// parseHookStdin reads a HookEvent from stdin (Claude Code sends JSON on stdin).
+func parseHookStdin() HookEvent {
+	var event HookEvent
+	json.NewDecoder(os.Stdin).Decode(&event)
+	return event
 }
 
 // runSetup adds vmux hooks to ~/.claude/settings.json (idempotent).