fix(discord): recall prior thread context after bot replies

[reefmind]

Summary

• allow Discord thread history backfill to continue past Hermes' last reply in threads
• skip Hermes-authored messages while recalling earlier human thread context
• add regression coverage for short follow-ups like “fix it” after Hermes previously answered it could not see history

Tests

• python -m pytest tests/gateway/test_discord_free_response.py -q
• python -m ruff check plugins/platforms/discord/adapter.py tests/gateway/test_discord_free_response.py
• python -m py_compile plugins/platforms/discord/adapter.py tests/gateway/test_discord_free_response.py

[alt-glitch]

This was generated by AI during triage.

Related: #42075 (skip bot messages in thread backfill) and #51414 (history_full_thread opt-in). Same goal (recall earlier human thread context past Hermes' last reply) but a different mechanism here: thread-scoped, config-gated (thread_history_recall / DISCORD_THREAD_HISTORY_RECALL, default on), and it segregates earlier-vs-recent context into separate windows. Not a duplicate — maintainer should pick among the competing approaches.

[teknium1]

Thanks for isolating the thread-history gap and adding a focused cold-start regression test.

Problems

• The new continuation branch does not work after a normal Hermes response. The unchanged after=_after_obj call at plugins/platforms/discord/adapter.py:4414 filters out messages at or before the cached self-message ID before the new if recall_thread_history branch at :4433 can see them. Current main stores that cache after normal sends at plugins/platforms/discord/adapter.py:2085-2092.
• The new regression test at tests/gateway/test_discord_free_response.py:682 does not seed _last_self_message_id, so it covers only the cache-miss path.

Suggested changes

• Disable or adjust the cached after boundary when recall is enabled, and add a cache-seeded regression case.
• Coordinate the default/configuration choice with the related approaches cited in the existing triage note (#42075 and #51414).

Automated hermes-sweeper review.

[teknium1]

This branch is unreachable for the normal hot path: the unchanged channel.history(..., after=_after_obj) above already excludes every message at or before _last_self_message_id, and normal sends populate that cache. Disable/adjust that after boundary when recall is enabled, then add a regression test that seeds _last_self_message_id.