A caller that joins a cold reservation no longer inherits another client's
RATE_LIMITED result. Once the rejected reservation is released it retries:
it either owns the next reservation and is admitted on its own quota, or joins
an admitted fetch. Adds a two-client regression (exhausted owner, available
joiner, exhausted joiner coalescing onto the admitted fetch).
Also drops the duplicate memory publication for a disk hit in the handler;
preflight already sets it, the handler only trims.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
