feat(gateway/discord): sync thread names with session titles

[TabooHarmony]

Auto-generated session titles (after the first exchange) and user-set titles via /title now propagate to Discord thread names.

Problem: Session titles are generated and stored in the local SQLite database, visible in /sessions list and the web dashboard. Discord thread names, however, are set once at thread creation and never updated. This creates a disconnect between the two.

Changes:

• DiscordAdapter.rename_thread() - edits thread names via discord.py
• After maybe_auto_title(), fire a lightweight async task that polls the session DB for up to 15s and renames the thread when the title appears
• Also sync immediately when /title is used

This bridges the gap between Hermes session titles and Discord thread names.

[alt-glitch]

Related to #13915 (opt-in smart auto-retitling for Discord threads) and #3009 — overlapping feature area. This PR takes the always-on approach vs #13915's opt-in config toggle.

[TabooHarmony]

Thanks for the context, wasn't aware of #13915.
The always-on approach here was intentional for minimal invasiveness (no new config keys, no user-facing toggles).
Happy to pivot this to an opt-in model or close it in favor of #13915 if that's the direction the maintainers prefer.

[teojs]

Very useful feature, looking forward to the developers merging it soon

[teknium1]

Thanks for addressing the disconnect between session titles and Discord threads. Current main has since landed the automatic-title half of this behavior via 0d9ed9214: gateway/run.py:19021-19026 passes a callback after auto-title generation, and gateway/run.py:13527-13572 limits retitles to Hermes-created auto-threads.

Problems

• The PR's generic Discord thread_id checks would rename pre-existing or human-renamed threads. Current main intentionally records auto-thread provenance and requires the original placeholder name before editing (plugins/platforms/discord/adapter.py:5403-5405, 5431-5437).
• The PR's code-point truncation is not safe for Discord's UTF-16 title limit; current main uses UTF-16-aware sanitization (plugins/platforms/discord/adapter.py:5417-5421, follow-up 1deeaf71a).
• The PR adds no regression tests for the async rename behavior.

Suggested changes

• Target the remaining explicit /title gap in gateway/slash_commands.py:3487-3504, and reuse the current guarded rename path rather than polling the session DB.
• Add coverage for explicit Discord /title plus preservation of human-renamed and pre-existing threads.

This is an automated hermes-sweeper review.

[alt-glitch]

This was generated by AI during triage.

Related to #26477 rather than a duplicate: this branch polls the session DB while #26477 uses a different title-sync path. The adapter was migrated to plugins/platforms/discord/adapter.py on main, and the branch also bundles unrelated reply_to delivery changes; please rebase/split before review.