fix: Slack thread routing — parse channel_id:thread_ts in send_message target

[dirtyren]

Problem

send_message(target='slack:C0B0GV4FKK7:1778181769.602679') was silently routing to the home channel (C0ATFHY907L) instead of channel C0B0GV4FKK7 in the specified thread.

Root Cause

Three separate bugs in tools/send_message_tool.py:

Bug 1 — _parse_target_ref regex miss (primary)
_SLACK_TARGET_RE = r'^\s*([CGD][A-Z0-9]{8,})\s*$' only matches bare channel IDs.
When target_ref = "C0B0GV4FKK7:1778181769.602679", the regex didn't match → returned (None, None, False) → fell through to channel-name resolution → fell back to home channel.

Bug 2 — _send_slack() missing thread_id param
Even if parsing had worked, _send_slack() had no thread_id parameter and never set thread_ts in the Slack API payload.

Bug 3 — _send_to_platform() not forwarding thread_id
The dispatch call await _send_slack(pconfig.token, chat_id, chunk) dropped thread_id entirely.

Fix

1. Added _SLACK_THREAD_TARGET_RE = re.compile(r'^\s*([CGD][A-Z0-9]{8,})':([\d.]+)\s*$') — handles CHANNEL_ID:THREAD_TS format (Slack timestamps use decimal notation like 1778181769.602679).
2. Updated _parse_target_ref to try the thread regex first, then fall back to bare-channel regex (no breakage of existing behaviour).
3. Added thread_id=None param to _send_slack() and inject payload["thread_ts"] = thread_id when set.
4. Passed thread_id=thread_id in _send_to_platform() dispatch.

Tests

• Updated existing assert_awaited_once_with assertion to include thread_id=None keyword arg.
• Added test_channel_with_thread_ts_is_parsed — verifies C0B0GV4FKK7:1778181769.602679 parses to (chat_id="C0B0GV4FKK7", thread_id="1778181769.602679", is_explicit=True).
• Added test_bare_channel_still_works_after_thread_regex — regression guard for bare channel ID path.

All 97 tests pass (pytest tests/tools/test_send_message_tool.py).

[alt-glitch]

Duplicate of #16992 (still open) — same fix: parse channel_id:thread_ts in Slack send_message target and plumb thread_ts through to the Slack API payload. Prior PRs #14146, #16962, #17741, #18911 all addressed the same issue.

[teknium1]

This appears to be implemented on current main now. Thanks for the useful duplicate fix and writeup — this automated hermes-sweeper review found the same behavior already landed.

Evidence:

• tools/send_message_tool.py:31 defines _SLACK_THREAD_TARGET_RE for Slack <conversation_id>:<thread_ts> targets.
• tools/send_message_tool.py:368 parses Slack thread targets before bare channel IDs and returns (chat_id, thread_id, True).
• tools/send_message_tool.py:784 forwards thread_id into _send_slack(..., thread_ts=thread_id).
• tools/send_message_tool.py:1064 / tools/send_message_tool.py:1078 make _send_slack() accept thread_ts and include it in the Slack chat.postMessage payload.
• tests/tools/test_send_message_tool.py:1230 covers a Slack thread target parse regression.
• The final plumbing landed in 74e845c000de1f32cd325758407ea706f18b7c36 and is contained in release tag v2026.6.5.