fix(qqofficial): allocate fresh msg_seq per inbound msg_id to avoid 40054005 dedup

QQ Official v2 API deduplicates passive messages by (msg_id, msg_seq).
The adapter reused msg_seq across multiple sends under the same inbound
msg_id, so multi-part text replies, rich media, and especially streaming
chunks (msg_seq pinned at 1) were rejected with:

  40054005 消息被去重，请检查请求msgseq

Add a per-inbound-msg_id sequence allocator (next_reply_msg_seq) on
QQOfficialClient, backed by a bounded OrderedDict + asyncio lock, and use
it for C2C/group text sends and rich media. Streaming now advances
ctx['msg_seq'] per chunk. Proactive sends (no msg_id) fall back to the
existing global counter.

Closes #2290

src/langbot/pkg/platform/adapters/qqofficial/adapter.py

@@ -280,6 +280,9 @@ class QQOfficialAdapter(QQOfficialAPIMixin, abstract_platform_adapter.AbstractPl
             ctx['stream_msg_id'] = resp['id']
         ctx['sent_length'] = len(ctx['accumulated_text'])
         ctx['index'] += 1
+        # 每个 chunk 单独 HTTP 下发，msg_seq 必须递增，否则后续 chunk 会被 QQ
+        # 以 (msg_id, msg_seq) 去重 (40054005 消息被去重)。
+        ctx['msg_seq'] += 1
         if is_final:
             self._stream_ctx.pop(message_id, None)
             self._stream_ctx_ts.pop(message_id, None)