feat: known-good CPU audio + 1080p VAAPI + KMS display wall

Working snapshot before the OpenVINO MetricGAN GPU spike:
thread-capped SpeechBrain DelaySum+MetricGAN on CPU, hop 200 ms,
video hold for A/V sync, Arc VAAPI H.264, headless kmssink wall.
32 tests passing. Do not treat this as a GPU audio path.

run.py

@@ -37,6 +37,10 @@ def worker_args_for(cfg, cam) -> list[str]:
         "--width", str(cfg.width),
         "--height", str(cfg.height),
         "--fps", str(cfg.fps),
+        "--bitrate", str(cfg.video_bitrate),
+        "--video-codec", cfg.video_codec,
+        "--video-encoder", cfg.video_encoder,
+        "--vaapi-device", cfg.vaapi_device,
         "--audio-rate", str(cfg.audio_rate),
         "--enhance-mode", cfg.enhance_mode,
         "--enhance-model", cfg.enhance_model,
@@ -59,6 +63,8 @@ class Supervisor:
     def spawn(self, cam) -> None:
         args = worker_args_for(self.cfg, cam)
         env = dict(os.environ)
+        env.setdefault("LIBVA_DRIVER_NAME", "iHD")
+        env.setdefault("LIBVA_DRM_DEVICE", self.cfg.vaapi_device)
         p = subprocess.Popen(
             [sys.executable, str(Path(__file__).parent / "run_worker.py"),
              *args],