[Fix] Prevent duplicate GitHub follow-up quotes

[roomote-roomote]

Opened on behalf of Daniel Riccio. Follow up by mentioning @roomote-roomote, in the web UI, or in Discord.

What changed

GitHub reply quotes are now claimed atomically before a comment write. A failed provider write restores the claim only when a newer follow-up has not replaced it.

Why this change was made

Concurrent comment writes could read the same pending web follow-up and quote it multiple times.

Impact

Each web follow-up is delivered at most once as a GitHub quote while preserving it for a retry after a failed write.

[roomote-roomote]

1 issue outstanding. See task

• packages/communication/src/messages.ts:439: SET ... NX only sees the current key. If an older write claims M, a newer follow-up N is claimed and posted successfully, then the older write fails, N has already deleted the key and this restores M. The next response quotes stale M after N, despite the newer follow-up having replaced it. Preserve a generation or tombstone for later claims so restore can reject superseded messages.
• packages/communication/src/messages.ts:57: If Redis executes the claim but its response is lost (or the API process stops) before claimLatestUserMessageForReplyQuote returns, the pending key has already been deleted and the 30-day claim is left behind. A retry creates a new token, cannot reclaim that stored message, and posts no quote, so the failed request loses the user's follow-up instead of preserving it for retry. Keep the pending message recoverable when acquisition itself fails, or make the claim safely resumable.

_{Reviewed eb23af0}