fix: rename Discord threads after auto-title

[ricatix]

Summary

• Rename Discord threads to the generated Hermes session title after auto-title completes
• Sanitize generated titles to Discord's 100-character thread name limit
• Also rename existing titled Discord thread sessions on the next response

Test Plan

• python -m py_compile gateway/run.py
• Manual Discord thread test: generated session title renamed the active thread

[alt-glitch]

Duplicate of tracking issue #18430 and existing open PRs #26477 / #15757 which implement the same Discord thread rename feature. Previously closed duplicates: #24311, #18429, #16059.

[ricatix]

Thanks for the context. I checked #18430, #26477, and #15757; this PR is indeed a subset/duplicate of the existing Discord thread/session-title sync work, especially #26477 which also covers manual /title sync and tests.

Closing this as duplicate. Thanks!

[ricatix]

Closing as duplicate of #18430 / #26477 / #15757.