iOS/tvOS playback could deadlock on PLAYBACK_RESTART: the event queue held
lifecycleLock across a synchronous mpv_get_property(time-pos) round-trip while
the core waited on the avfoundation VO, which itself waits on the main thread;
the main thread meanwhile blocked on lifecycleLock in isLifecycleActive.
Snapshot the handle under the lock and query without it. The read stays on the
serial event queue, which also serializes destruction, so the handle cannot be
torn down mid-read.
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