Repair the compensating half of the OPFS put saga.
The coordinator now owns a single abortPreparedPut() driven by a
composition-owned bounded signal instead of the caller's already aborted one,
and the worker client no longer issues a duplicate fire-and-forget abort.
Journal rows and budget reservations are released only after the physical
effect is confirmed CLEANED or ALREADY_CLEAN; a timeout, malformed response or
EFFECT_UNKNOWN keeps PREPARING/FILES_READY and returns OBJECT_RECONCILE.
New writes carry a transaction-unique physicalGenerationId through the staging
receipt, manifest path and prepared object, so a late compensation deletes only
its own transaction's directory even when a newer transaction legitimately
reuses the same logical generation. v1 paths, receipts and prepared objects stay
readable through the rollback window.
Abort and cleanup hold the origin mutation lease through physical deletion and
staging removal. A transaction that never reached staging returns ALREADY_CLEAN
without waiting for the lease, which would otherwise deadlock against the BEGIN
it is cancelling.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
