Fix GitHub Actions simulator streaming

[DjDeveloperr]

Summary

• make the private SimulatorKit screen attach path work on hosted runners
• add WebRTC diagnostics and latest-frame streaming behavior for slow remote links
• harden software H.264 handling around native frame copies and VideoToolbox scaler failures

Notes

This PR uses the already-pushed fix/provider-screen-adapter branch. Local uncommitted ffmpeg/libx264 experiments are intentionally not included.

Testing

• Built SimDeck CLI/client during GitHub Actions provider experiments
• Exercised Macrodex provider workflow against this branch
• Ran standalone VideoToolbox encode probes on GitHub Actions to validate hardware encode availability/perf constraints