Add Discord thread title auto-rename after session naming

[0fflineDocs]

Summary

This adds Discord thread renaming support so auto-generated session titles can update the backing Discord thread name after the title is produced.

Changes

• add rename_thread(thread_id, new_name) to the Discord platform adapter
• add scheduled Discord thread title rename wiring in gateway/run.py
• connect Discord thread sessions to maybe_auto_title(..., title_callback=...)
• add tests covering:
  • cached thread rename
  • fetch fallback
  • 100-character truncation
  • scheduler invocation
  • invalid thread IDs ignored safely

Why

Previously, auto-titling could generate a better session title internally, but Discord thread names were not updated to match. This left Discord threads with stale or generic names even when the agent had already produced a stronger title.

Validation

bash
pytest -q tests/gateway/test_discord_thread_title_rename.py tests/gateway/test_telegram_topic_mode.py -q

[alt-glitch]

Duplicate of #15757 — same feature (sync Discord thread names with auto-generated session titles). See also tracking issue #18430.

[0fflineDocs]

Duplicate of #15757 — same feature (sync Discord thread names with auto-generated session titles). See also tracking issue #18430.

Thanks let's close this.