[eugene-mux]

Description

Fix the missing standardized-file failure after force quit and relaunch. The patch addresses purgeable temporary storage, deletion after a recoverable transport failure, and saved SDK paths from a previous app container. There are no public SDK API changes.

Changes

• Retain standardized payloads in Application Support, excluded from backup; preserve uploads.json and move surviving legacy payloads without re-encoding or changing their checkpoint.
• Transfer output ownership at transport commit. Persistence owns deletion after commit and writes record removal before deleting bytes.
• Reclaim old, unreferenced generated files on cache open using the real process start time; cleanup is best-effort and handles symlinked paths.
• Report a missing saved file using the existing .file kind with explicit new-upload-URL guidance. Wire the example's startup delegate/restore/start flow and durable picker input.

Validation

• 194 tests passed on macOS and iOS Simulator. 33 restore/persistence Thread Sanitizer tests passed.
• Physical-device example build, version consistency, and diff checks passed.
• Physical-device acceptance of this simplified commit remains pending; earlier full-recovery device results do not count.

Deferred

The broader implementation is preserved on em/nat-581-recovery-full. Deferred work: error/API additions; transport offsets, Range, retry/backoff and final-chunk handling; retry/restart/cancel and public pause-state semantics; recovery during conversion; and H264 SPS parsing. None are included in this patch. No version bump is included.

NAT-581