fix: add telegram.request mock and discovery fixture to remaining test files

The original PR missed test_dm_topics.py and
test_telegram_network_reconnect.py — both need the telegram.request
mock module. The reconnect test also needs _no_auto_discovery since
_handle_polling_network_error calls connect() which now invokes
discover_fallback_ips().

tests/gateway/test_dm_topics.py

@@ -32,7 +32,7 @@ def _ensure_telegram_mock():
     telegram_mod.constants.ChatType.CHANNEL = "channel"
     telegram_mod.constants.ChatType.PRIVATE = "private"
 
-    for name in ("telegram", "telegram.ext", "telegram.constants"):
+    for name in ("telegram", "telegram.ext", "telegram.constants", "telegram.request"):
         sys.modules.setdefault(name, telegram_mod)
 
 

tests/gateway/test_telegram_network_reconnect.py

@@ -27,7 +27,7 @@ def _ensure_telegram_mock():
     telegram_mod.constants.ChatType.CHANNEL = "channel"
     telegram_mod.constants.ChatType.PRIVATE = "private"
 
-    for name in ("telegram", "telegram.ext", "telegram.constants"):
+    for name in ("telegram", "telegram.ext", "telegram.constants", "telegram.request"):
         sys.modules.setdefault(name, telegram_mod)
 
 
@@ -36,6 +36,14 @@ _ensure_telegram_mock()
 from gateway.platforms.telegram import TelegramAdapter  # noqa: E402
 
 
+@pytest.fixture(autouse=True)
+def _no_auto_discovery(monkeypatch):
+    """Disable DoH auto-discovery so connect() uses the plain builder chain."""
+    async def _noop():
+        return []
+    monkeypatch.setattr("gateway.platforms.telegram.discover_fallback_ips", _noop)
+
+
 def _make_adapter() -> TelegramAdapter:
     return TelegramAdapter(PlatformConfig(enabled=True, token="test-token"))