Give snapshot capture, header admission, packed members, and container streams one file-handle owner. Serialize adoption with reader shutdown, retain failed closes for retry, and remove snapshots only after descriptor cleanup succeeds.
Cover unread members, pending opens, zero-byte members, and paired format/cleanup failures. Keep intentionally unrecoverable test fixtures hygienic and strengthen managed identity and process cleanup-authority expectations.
Validation: full npm run check; 99 targeted tests and temporary-directory hygiene; exact discovery of 877 test files. No real vendor-provider verification was performed.