fix(gateway): stream consumer first message drops thread context

Cherry-picked from PR #13077 commits:
- 5500c7d8 fix(gateway): stream consumer first message drops thread context
- e84403b9 test(gateway): add regression tests for stream consumer thread routing

Fixes: Streaming first message drops thread/topic context in Feishu group
topics, Slack threads, Telegram forum topics. Adds initial_reply_to_id
ctor arg to GatewayStreamConsumer, threaded through _send_or_edit and
_send_new_chunk. Also fixes Feishu _send_raw_message fallback path
(reply -> create) to use receive_id_type='thread_id' so the new message
lands in the correct topic instead of the main channel.

Authored by hrygo via PR #13077 (re-attributed from the bot-authored
salvage commit on the original branch).

gateway/stream_consumer.py

@@ -92,6 +92,7 @@ class GatewayStreamConsumer:
         config: Optional[StreamConsumerConfig] = None,
         metadata: Optional[dict] = None,
         on_new_message: Optional[callable] = None,
+        initial_reply_to_id: Optional[str] = None,
     ):
         self.adapter = adapter
         self.chat_id = chat_id
@@ -105,6 +106,7 @@ class GatewayStreamConsumer:
         # the content, not edit the old bubble above it.
         # Called with no arguments. Exceptions are swallowed.
         self._on_new_message = on_new_message
+        self._initial_reply_to_id = initial_reply_to_id
         self._queue: queue.Queue = queue.Queue()
         self._accumulated = ""
         self._message_id: Optional[str] = None
@@ -1004,10 +1006,12 @@ class GatewayStreamConsumer:
                     # The final response will be sent by the fallback path.
                     return False
             else:
-                # First message — send new
+                # First message — send new, threaded to the original user message
+                # so it lands in the correct topic/thread.
                 result = await self.adapter.send(
                     chat_id=self.chat_id,
                     content=text,
+                    reply_to=self._initial_reply_to_id,
                     metadata=self.metadata,
                 )
                 if result.success: