Refactor viewer initialization and protocol.

Introduced a ViewerConfig dataclass to encapsulate common viewer window parameters. The NativeViewer now accepts a ViewerConfig and no longer requires a model at initialization. The Viewer protocol has been updated to include a close method (renamed from stop) and an upload_image method. Added checks for None models/data in studio event handling.

PiperOrigin-RevId: 939631378
Change-Id: Ibc07d0e775efa0d79ce5552ee52102e943a9b290

python/mujoco/experimental/studio/studio.py

@@ -30,12 +30,12 @@ def main(argv: list[str]) -> None:
   app = studio_app.StudioApp.from_argv(argv)
 
   # Initialize the viewer.
-  viewer = native_viewer.NativeViewer(
-      app.model,
+  config = viewer_protocol.ViewerConfig(
       width=_WIDTH.value,
       height=_HEIGHT.value,
       gfx=_GFX.value,
   )
+  viewer = native_viewer.NativeViewer(config)
 
   # Main viewer loop.
   while viewer.is_running():