fix(telegram): respect reply_to_mode for DM topic reply fallback

The DM topic reply fallback code in send() hardcoded should_thread=True
when telegram_dm_topic_reply_fallback metadata was present, bypassing
_should_thread_reply() and ignoring reply_to_mode config. This caused
quote bubbles on every response even with reply_to_mode: 'off'.

Fix:
- Add reply_to_mode param to _reply_to_message_id_for_send() and
  _thread_kwargs_for_send() classmethods
- In send(), check self._reply_to_mode != 'off' for DM topic fallback
- Suppress reply anchor and reply_to_message_id when mode is 'off'
  while preserving message_thread_id for correct topic routing
- Thread reply_to_mode through all 29 call sites

Regression coverage: 10 new tests in test_telegram_reply_mode.py
covering classmethod behavior, send() integration, and backward
compatibility.

Fixes reply_to_mode: 'off' ignored by Telegram DM topic reply fallback code #23994

tests/gateway/test_telegram_reply_mode.py

@@ -304,3 +304,110 @@ class TestTelegramYamlConfigLoading:
         load_gateway_config()
 
         assert os.environ.get("TELEGRAM_REPLY_TO_MODE") == "all"
+
+
+class TestDMTopicFallbackReplyToMode:
+    """Tests for reply_to_mode enforcement on DM topic fallback paths.
+
+    Regression tests for https://github.com/NousResearch/hermes-agent/issues/23994:
+    reply_to_mode 'off' was ignored when sending via Hermes-created DM topic
+    lanes (telegram_dm_topic_reply_fallback metadata), causing quote bubbles
+    despite the user setting reply_to_mode: 'off'.
+    """
+
+    DM_TOPIC_METADATA = {
+        "thread_id": "42",
+        "telegram_dm_topic_reply_fallback": True,
+        "telegram_reply_to_message_id": "12345",
+    }
+
+    # -- _reply_to_message_id_for_send classmethod --
+
+    def test_reply_to_id_suppressed_when_off(self):
+        """reply_to_mode='off' suppresses reply anchor for DM topic fallback."""
+        result = TelegramAdapter._reply_to_message_id_for_send(
+            None, self.DM_TOPIC_METADATA, reply_to_mode="off",
+        )
+        assert result is None
+
+    def test_reply_to_id_returned_when_first(self):
+        """reply_to_mode='first' still returns reply anchor for DM topic fallback."""
+        result = TelegramAdapter._reply_to_message_id_for_send(
+            None, self.DM_TOPIC_METADATA, reply_to_mode="first",
+        )
+        assert result == 12345
+
+    def test_reply_to_id_returned_when_all(self):
+        """reply_to_mode='all' still returns reply anchor for DM topic fallback."""
+        result = TelegramAdapter._reply_to_message_id_for_send(
+            None, self.DM_TOPIC_METADATA, reply_to_mode="all",
+        )
+        assert result == 12345
+
+    def test_reply_to_id_returned_when_no_mode(self):
+        """Without reply_to_mode, behavior is unchanged (backward compat)."""
+        result = TelegramAdapter._reply_to_message_id_for_send(
+            None, self.DM_TOPIC_METADATA,
+        )
+        assert result == 12345
+
+    def test_explicit_reply_to_overrides_mode(self):
+        """Explicit reply_to param always wins, regardless of mode."""
+        result = TelegramAdapter._reply_to_message_id_for_send(
+            "999", self.DM_TOPIC_METADATA, reply_to_mode="off",
+        )
+        assert result == 999
+
+    # -- _thread_kwargs_for_send classmethod --
+
+    def test_thread_kwargs_suppressed_reply_anchor_when_off(self):
+        """reply_to_mode='off' returns thread_id without reply anchor."""
+        result = TelegramAdapter._thread_kwargs_for_send(
+            "100", "42", self.DM_TOPIC_METADATA,
+            reply_to_message_id=None, reply_to_mode="off",
+        )
+        assert result == {"message_thread_id": 42}
+
+    def test_thread_kwargs_returns_full_when_first(self):
+        """reply_to_mode='first' returns thread_id (reply anchor in send kwargs)."""
+        result = TelegramAdapter._thread_kwargs_for_send(
+            "100", "42", self.DM_TOPIC_METADATA,
+            reply_to_message_id=12345, reply_to_mode="first",
+        )
+        assert result == {"message_thread_id": 42}
+
+    def test_thread_kwargs_no_mode_backward_compat(self):
+        """Without reply_to_mode, behavior is unchanged."""
+        result = TelegramAdapter._thread_kwargs_for_send(
+            "100", "42", self.DM_TOPIC_METADATA,
+            reply_to_message_id=12345,
+        )
+        assert result == {"message_thread_id": 42}
+
+    # -- send() integration test --
+
+    @pytest.mark.asyncio
+    async def test_send_dm_topic_off_no_quote(self, adapter_factory):
+        """send() with DM topic fallback and reply_to_mode='off' skips reply."""
+        adapter = adapter_factory(reply_to_mode="off")
+        adapter._bot = MagicMock()
+        adapter._bot.send_message = AsyncMock(return_value=MagicMock(message_id=1))
+        adapter.truncate_message = lambda content, max_len, **kw: ["chunk1"]
+
+        await adapter.send("12345", "test content", metadata=self.DM_TOPIC_METADATA)
+
+        call = adapter._bot.send_message.call_args_list[0]
+        assert call.kwargs.get("reply_to_message_id") is None
+
+    @pytest.mark.asyncio
+    async def test_send_dm_topic_first_still_quotes(self, adapter_factory):
+        """send() with DM topic fallback and reply_to_mode='first' still quotes."""
+        adapter = adapter_factory(reply_to_mode="first")
+        adapter._bot = MagicMock()
+        adapter._bot.send_message = AsyncMock(return_value=MagicMock(message_id=1))
+        adapter.truncate_message = lambda content, max_len, **kw: ["chunk1"]
+
+        await adapter.send("12345", "test content", metadata=self.DM_TOPIC_METADATA)
+
+        call = adapter._bot.send_message.call_args_list[0]
+        assert call.kwargs.get("reply_to_message_id") == 12345