The /compact the composer sends before a message to an idle thread now
carries idleCompaction: "onReturn" (T3 Code's own compaction before cache
expiry carries "beforeCacheExpires"). The working row reads "Compacting
after being idle…" while it runs, the finished divider notes "After being
idle", and the compaction no longer sends its own Done notification ahead
of the reply to your message.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>