test nit: unused var in deadman ping test

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/unit/test_qabot_deadman.py

@@ -64,6 +64,6 @@ def test_nightly_ping_once_after_2030():
 
 
 def test_nightly_ping_flags_a_day_with_no_events():
-    dm, st = make(TUE_EVENING, datetime(2026, 7, 6, 15, 59))  # last event yesterday
+    dm, _ = make(TUE_EVENING, datetime(2026, 7, 6, 15, 59))  # last event yesterday
     msg = dm.check()
     assert msg is not None and "NO events today" in msg