feat(gateway): Feishu auto-thread and topic-based session routing

[keenlin]

What does this PR do?

Closes #9154

Problem: Discord is inaccessible in China, leaving users without a thread-isolated gateway
option. This PR implements auto-thread and topic-based session isolation,
filling that gap.

Platform adaptation note: Feishu lacks Discord's explicit thread creation API. We
use a placeholder message as a compensating pattern — sending "🔄 Thinking..." with
reply_in_thread=true forces topic creation, allowing the first message to route into
the correct thread session.

Key Features:

• FEISHU_AUTO_THREAD: Auto-create topics for group mentions (like
  DISCORD_AUTO_THREAD)
• Topic session isolation: Each Feishu topic has independent conversation context
  (intrinsic, no toggle)
• FEISHU_THREAD_REQUIRE_MENTION: Control mention requirements in bot-participated
  topics
• Placeholder bootstrap: Sends "🔄 Thinking..." first, edits with actual response

Discord Alignment:

Feature	Discord	Feishu (this PR)
Auto-thread env	DISCORD_AUTO_THREAD	FEISHU_AUTO_THREAD
Exclusion list	DISCORD_NO_THREAD_CHANNELS	FEISHU_NO_THREAD_GROUPS
Thread tracking	_bot_participated_threads	Same pattern
Session isolation	Thread = isolated session	Topic = isolated session

Changes Made

• gateway/platforms/feishu.py: Auto-thread bootstrap, root_id session routing,
  thread tracking persistence
• hermes_cli/config.py: Register new env vars
• tests/gateway/test_feishu.py: Thread routing tests
• website/docs/user-guide/messaging/feishu.md: Thread Routing documentation

How to Test

# 1. Auto-thread flow
export FEISHU_AUTO_THREAD=true
hermes gateway --platform feishu
# Mention bot in group → should create topic with placeholder → edit with response

# 2. Topic isolation
# Messages in same topic share context, different topics are isolated

# 3. Run tests
pytest tests/gateway/test_feishu.py -v -k "thread"

Type of Change

• ✨ New feature

Checklist

• Follows Conventional Commits
• Added tests
• Updated documentation
• Zero gateway layer changes (adapter-only)

[keenlin]

Latest version broke this PR—converting to draft while investigating regression.

---

GatewayStreamConsumer/interim messages could send with thread_id but no reply_to, which fell back to CreateMessage and posted to the parent group. This follow-up fix routes those thread-context sends through the Reply API so they stay inside the topic.

[teknium1]

Thanks for the detailed adapter work and the follow-up addressing interim thread-context sends.

This automated hermes-sweeper review is closing the PR under the standing configuration policy:

• The diff introduces FEISHU_AUTO_THREAD, FEISHU_NO_THREAD_GROUPS, and FEISHU_THREAD_REQUIRE_MENTION as user-facing behavioral controls (hermes_cli/config.py, PR head a79920f47569).
• AGENTS.md:102-107 requires non-secret behavior settings to use config.yaml, rather than new HERMES_*/environment-variable configuration.
• The current gateway already has a plugin-owned YAML configuration bridge (gateway/config.py:1252-1287; Feishu registers it at plugins/platforms/feishu/adapter.py:5618-5654).

Please re-scope any follow-up around platforms.feishu.extra configuration through that YAML path. It should also preserve thread_id as the topic identity rather than prioritizing root_id; related report #20548 documents why those fields can diverge.

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Closed as not-planned per standing maintainer policy (env-var-for-config). This is a design-direction decision, not a code-quality judgment — see the Contribution Rubric in AGENTS.md for what the project is looking for. If you believe this policy was misapplied to your change, comment here and a maintainer will take a look.