fix(send_message): normalize Telegram General topic thread_id + add Slack thread_ts

Addresses two review findings from Codex:

1. telegram:current breaks in forum General — the gateway synthesizes
   thread_id='1' for the General topic, but the Bot API rejects
   message_thread_id=1. Strip it to None in _resolve_current_session_target(),
   matching TelegramAdapter._message_thread_id_for_send().

2. slack:current drops thread context — _send_slack() never received
   thread_id and posted chat.postMessage without thread_ts, so messages
   landed in channel root instead of the active thread. Add thread_id
   param and forward it as thread_ts when present.

Tests: 4 new cases (Telegram General normalization, real topic preserved,
Slack thread_ts included, Slack thread_ts absent). 84 passed total.

tests/tools/test_send_message_tool.py

@@ -1900,6 +1900,7 @@ class TestSendMessageCurrentSessionTarget:
             )
 
         assert result["success"] is True
+        # thread_id must be None (stripped), not "1"
         send_mock.assert_awaited_once_with(
             Platform.TELEGRAM,
             telegram_cfg,
@@ -1970,6 +1971,7 @@ class TestSendSlackThreadId:
             )
 
         assert result["success"] is True
+        # Verify thread_ts was in the JSON payload
         call_kwargs = mock_session.post.call_args
         payload = call_kwargs.kwargs.get("json") or call_kwargs[1].get("json")
         assert payload["thread_ts"] == "1712345678.1234"

tools/send_message_tool.py

@@ -355,6 +355,13 @@ def _resolve_current_session_target(platform_name: str):
             None,
         )
 
+    # Telegram forum chats synthesize thread_id="1" for the General topic,
+    # but the Bot API rejects message_thread_id=1. The gateway adapter
+    # normalizes this away (TelegramAdapter._message_thread_id_for_send);
+    # mirror that here so telegram:current doesn't break in General.
+    if platform_name == "telegram" and session_thread_id == "1":
+        session_thread_id = None
+
     return None, session_chat_id, session_thread_id
 
 
@@ -577,7 +584,7 @@ async def _send_to_platform(platform, pconfig, chat_id, message, thread_id=None,
     last_result = None
     for chunk in chunks:
         if platform == Platform.SLACK:
-            result = await _send_slack(pconfig.token, chat_id, chunk)
+            result = await _send_slack(pconfig.token, chat_id, chunk, thread_id=thread_id)
         elif platform == Platform.WHATSAPP:
             result = await _send_whatsapp(pconfig.extra, chat_id, chunk)
         elif platform == Platform.SIGNAL:
@@ -966,7 +973,7 @@ async def _send_discord(token, chat_id, message, thread_id=None, media_files=Non
         return _error(f"Discord send failed: {e}")
 
 
-async def _send_slack(token, chat_id, message):
+async def _send_slack(token, chat_id, message, thread_id=None):
     """Send via Slack Web API."""
     try:
         import aiohttp
@@ -980,6 +987,8 @@ async def _send_slack(token, chat_id, message):
         headers = {"Authorization": f"Bearer {token}", "Content-Type": "application/json"}
         async with aiohttp.ClientSession(timeout=aiohttp.ClientTimeout(total=30), **_sess_kw) as session:
             payload = {"channel": chat_id, "text": message, "mrkdwn": True}
+            if thread_id:
+                payload["thread_ts"] = thread_id
             async with session.post(url, headers=headers, json=payload, **_req_kw) as resp:
                 data = await resp.json()
                 if data.get("ok"):