fix(discord): auto-thread free-response channels

[andyylin]

Summary

• adds deterministic smart names for Discord auto-created threads
• keeps discord.free_response_channels from disabling auto-thread creation
• preserves discord.no_thread_channels as the explicit auto-thread opt-out
• retitles Discord auto-thread sessions after the first exchange when smart thread titles are enabled
• hardens Discord auto-thread tests against host env leakage

Runtime verification

• Confirmed in the live Discord gateway after restart: a newly created thread used the smarter title path instead of the raw first-message slice.

Test plan

• python -m pytest tests/agent/test_title_generator.py tests/gateway/test_discord_slash_commands.py -q -o 'addopts=' — 62 passed
• Discord live smoke test: new auto-created thread title looked correct

[andyylin]

Pushed follow-up commit 16dcd437e to retitle Discord auto-thread sessions after the first exchange. Local targeted tests pass: python -m pytest tests/agent/test_title_generator.py tests/gateway/test_discord_slash_commands.py -q -o 'addopts=' → 62 passed. Runtime smoke check from live Discord also looks good: a new thread used the smart title path.

[andyylin]

CI failure fix pushed.

Root cause: the PR branch had drifted behind current main; after rebasing, CI exposed stale expectations outside the original Discord title patch:

• Discord free-response tests still expected free-response channels to skip auto-threading, but the PR behavior is intentionally: bypass mention gating while still auto-threading top-level messages.
• ACP/TUI/concurrent-interrupt/gateway-restart/Teams/Dockerfile expectations had moved with main.

Fix:

• Rebases PR fix(discord): auto-thread free-response channels #18592 onto current origin/main.
• Updates the Discord free-response regression test to assert top-level free-response messages are dispatched through the auto-created thread.
• Aligns affected tests/compat code with current CI behavior.
• Adds a pending-title cleanup guard in the TUI gateway deferred session build path.

Local verification:

• 84 passed in 2.63s for title + Discord targeted suite.
• 365 passed in 13.34s for the previously failing-area suite.

Pushed commit: 3d8c57c0d702c333768158f7b8d218b9784dd95b.

[teknium1]

Thanks for the Discord coverage and the live verification.

Problems

• The free-response change conflicts with current behavior and stated intent: plugins/platforms/discord/adapter.py:6223 keeps is_free_channel in skip_thread, while website/docs/user-guide/messaging/discord.md:377 documents inline replies for free-response channels. Commit d55754456 added that guard specifically to prevent a thread per free-response message.
• The semantic-title work is now provided by 0d9ed9214: auto-created-thread provenance is carried by plugins/platforms/discord/adapter.py:5355-5359,6338-6342, and gateway/run.py:13527-13610,19021-19026 retitles after the first exchange without overwriting a human rename.

Suggested changes

• Preserve the current free-response inline policy unless maintainers choose a documented design change. Any remaining title issue should be re-scoped to a verified gap in the current semantic-title path.

Automated hermes-sweeper review.

[teknium1]

This reverses the later explicit free-response contract. Current main retains or is_free_channel in the active adapter (plugins/platforms/discord/adapter.py:6223); commit d55754456 and website/docs/user-guide/messaging/discord.md:377 define free-response channels as intentionally inline to avoid creating one thread per message.

[andyylin]

Closing because current upstream intentionally keeps free-response channels inline, while the still-useful semantic-title behavior has already landed separately. The remaining patch is obsolete and conflicts with documented behavior.