3f509ebc5c
Measured ~5× faster boot under --ui (~12 → ~63 MIPS) by moving the per-frame PM4 drain (draws, YUV texture decode, resolves) + UI publish off the emulation thread onto the GPU worker — canary's async-command-thread model. User-confirmed visuals identical to the inline path (splash + intro video render correctly). Flip the default: `--ui` now uses the threaded GPU backend. Opt back to inline with `--gpu-inline` or `XENIA_UI_GPU_INLINE=1`. The deterministic golden path already passes `--gpu-inline`, so goldens are unaffected (n2m re-checked MATCH). `XENIA_UI_GPU_THREAD` retained as a no-op alias. Headless default (M1.9 threaded) unchanged. Note: threading the GPU only helps GPU-bound phases (boot). The intro VIDEO is CPU-bound on multi-threaded 720p-YUV software decode (FP-arith-heavy, mostly JIT fallback), so it stays ~real-video-length; that needs the multi-core / native-FP levers, not GPU threading.