fix: repair broken tests across alert, chanmgmt, and integration

- test_alert: remove stale _MAX_ANNOUNCE import/test, update _errors
  assertions for per-backend dict, fix announcement checks (action vs
  send), mock _fetch_og_batch in seeding tests, fix YouTube/SearX mock
  targets (urllib.request.urlopen), include keyword in fake data titles
- test_chanmgmt: add _FakeState to _FakeBot (on_invite now persists)
- test_integration: update help assertion for new output format

696 tests pass, 0 failures.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_integration.py

@@ -227,8 +227,8 @@ class TestCommandDispatch:
 
         replies = h.sent_privmsgs("#test")
         assert len(replies) == 1
-        assert "Commands:" in replies[0]
-        assert "!ping" in replies[0]
+        assert "help" in replies[0]
+        assert "ping" in replies[0]
 
     def test_unknown_command_ignored(self):
         """Unknown commands produce no reply."""