* docs: add Configuration Options section to Slack docs
Documents all config.yaml options for the Slack bot:
- Thread & reply behavior (reply_to_mode, reply_broadcast)
- Session isolation (group_sessions_per_user)
- Mention & trigger behavior (require_mention, mention_patterns, reply_prefix)
- Unauthorized user handling (unauthorized_dm_behavior)
- Voice transcription (stt_enabled)
- Full example config showing all options together
Includes a note about Slack's hardcoded @mention requirement in channels
(no free_response_channels equivalent like Discord/Telegram).
* docs: consolidate reply_in_thread into Configuration Options section
Folds the standalone Reply Threading subsection from PR #4643 into
the Thread & Reply Behavior subsection, keeping all config options
in one place. Adds reply_in_thread to the table and full example.
798a7b99e4