refactor: route the /loop wakeup send through _notif_submit

The hand-rolled try/except around message.start + _run_prompt_submit
duplicated _notif_submit, which already emits the start event, submits,
and releases the claimed turn on failure (and logs why). One release
path per claim site keeps the leak fix in one place.

tui_gateway/session_notifications.py

@@ -189,12 +189,8 @@ def _notif_slash_loop_tick(rid: str, sid: str, session: dict, mgr, wakeup: str)
             if not _notif_claim_turn(session):
                 mgr.abandon_tick()
                 return
-            try:
-                _emit("message.start", sid)
-                _run_prompt_submit(rid, sid, session, payload["message"])
-            except Exception:
-                _notif_release_turn(session)  # the swallow below would otherwise leave the session busy for good
-                raise
+            # Releases the claim on failure: the swallow below would otherwise leave the session busy for good.
+            _notif_submit(rid, sid, session, payload["message"], "loop wakeup send failed")
             return
     except Exception:
         pass