Renamed the notion of handler classes to plugin classes in the Studio Python API

This change refactors the Python API to use the term "plugins" instead of "handlers" for classes containing decorated handler methods. The term handler is still used for an annotated method of a plugin class that handles a specific message type. Also improved some documentation.

PiperOrigin-RevId: 962150099
Change-Id: I34a8cc410cd784b088605490cfa3baccea5c9e71

python/mujoco/experimental/studio/native_viewer.py

@@ -13,9 +13,8 @@
 # limitations under the License.
 """Simulation-agnostic native viewer for MuJoCo models.
 
-See the documentation for studio_app.py for more details on the architecture
-separating the viewer and simulation. See the sample/ folder for examples of how
-to use these classes.
+See the documentation for viewer_app.py for more details on the architecture
+separating the viewer and simulation.
 """
 
 from typing import Any
@@ -40,7 +39,7 @@ class NativeViewer(viewer_protocol.Viewer):
       *,
       model: mujoco.MjModel | None = None,
       model_path: str = '',
-      handlers: list[Any] | None = None,
+      plugins: list[Any] | None = None,
       camera: mujoco.MjvCamera | None = None,
       vis_options: mujoco.MjvOption | None = None,
       perturb: mujoco.MjvPerturb | None = None,
@@ -54,7 +53,7 @@ class NativeViewer(viewer_protocol.Viewer):
       endpoint: The viewer endpoint for communication with the sim side.
       model: Optional initial MjModel. Forwarded to the base Viewer.
       model_path: Optional path to the model file.
-      handlers: Optional list of handler instances.
+      plugins: Optional list of plugin instances.
       camera: Camera parameters. Internal object is created if None.
       vis_options: Visualization options. Internal object is created if None.
       perturb: Perturbation parameters. Internal object is created if None.
@@ -66,7 +65,7 @@ class NativeViewer(viewer_protocol.Viewer):
         endpoint,
         model=model,
         model_path=model_path,
-        handlers=handlers,
+        plugins=plugins,
         camera=camera,
         vis_options=vis_options,
         perturb=perturb,