Greptile Summary

This PR replaces unsynchronized mutable state in PhotoCaptureDelegate, MovieFileDelegate, and GatewayTLSFingerprintProbe with OSAllocatedUnfairLock-protected state, correctly eliminating data races that existed when AVFoundation/URLSession delegate callbacks fired concurrently with timeout handlers or each other.

Key changes:

• PhotoCaptureDelegate and MovieFileDelegate: private var didResume = false becomes private let resumed = OSAllocatedUnfairLock(initialState: false). The check-and-set is now atomic via withLock, preventing double-resumption of a CheckedContinuation.
• GatewayTLSFingerprintProbe: three separate unguarded mutable vars (didFinish, session, task) are consolidated into a ProbeState struct protected by a single OSAllocatedUnfairLock. The finish() method now atomically checks the flag and drains the session/task references under the lock before cancelling/invalidating outside it — a clean improvement over the previous objc_sync_enter/objc_sync_exit approach that also avoids holding the lock during I/O teardown.

The import Observation already in the file implies a deployment target ≥ iOS 17, so OSAllocatedUnfairLock (available from iOS 16) is available without any #available guard.

Confidence Score: 5/5

• This PR is safe to merge — changes are narrowly scoped, mechanically correct, and strictly improve thread safety without altering observable behavior.
• The lock usage follows the correct check-and-set pattern throughout. OSAllocatedUnfairLock is appropriate for the use-case (short, non-blocking critical sections), no re-entrant lock acquisitions exist, and clearing session/task inside the lock before cancelling outside it is both correct and an improvement over the prior code. Deployment target is confirmed ≥ iOS 17 via existing import Observation, so no availability concern.
• No files require special attention.

_{Last reviewed commit: 2d676d6}

Superseded by #33241 after this PR auto-closed when its base branch was deleted. Equivalent concurrency-lock scope was landed in #33241 (merge commit 6df57d9).