Add experimental session replay capturing on iOS (UE 5.8+)

[tustanivsky]

This PR adds session replay capturing support on iOS, extending the existing desktop (Windows/Mac/Linux) crash-replay feature to mobile Apple devices.

When Attach session replay is enabled, the plugin records a rolling gameplay clip by capturing the backbuffer, encoding it to H.264 via the engine's AVCodecs abstraction (hardware VideoToolbox on iOS), and muxing it into a fragmented MP4 on disk. If the app crashes, the clip is uploaded as a video/mp4 attachment to the crash event on the next launch, reusing the existing sentry-cocoa onLastRunStatusDetermined upload flow that was already in place for macOS.

Example crash event with session replay attached captured on iOS.

Key changes

• Moved the session replay recorder from FMacSentrySubsystem into the shared FAppleSentrySubsystem base so macOS and iOS use the same recorder lifecycle, replay file path handling, and next-launch upload logic.
• Extended the Apple-specific (VideoToolbox/Metal) code paths in the recording pipeline from PLATFORM_MAC to PLATFORM_APPLE:
  • encoder pool textures are created with ETextureCreateFlags::CPUReadback (required by the engine's RHI→Metal resource transform; without it VideoToolbox rejects every frame) with the extra copy pass Metal requires
  • microsecond SendFrame timestamp scale, CABAC entropy workaround, and the hourly encoder restart guarding the uint32 PTS wrap
• Opened the encoder with swapped width/height when the backbuffer arrives transposed relative to the app's screen orientation
• Refactored the session replay platform gate in Sentry.Build.cs into IsSessionReplaySupported(), enabling iOS behind UE_5_8_OR_LATER.
• Enabled AVCodecsCore and VTCodecs for IOS in the sample project.

Known Limitations

iOS support requires Unreal Engine 5.8 or newer - UE 5.8 is the first release where the (still experimental) AVCodecs plugin suite allowlists iOS - VTCodecs (VideoToolbox H.264 hardware encoding) and its RHI integration were previously Mac-only. On older engine versions the plugin builds as before, with session replay capturing unavailable on iOS.

Documentation

• docs(unreal): Session Replay capturing on iOS sentry-docs#18636

Related items:

• Add experimental session replay capturing on Windows #1404
• Add experimental Session Replay capturing on Mac #1425
• Add experimental session replay capturing on Linux #1428
• Add experimental session replay capturing for Android #1386

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