The mcpforunity://editor/prefab-stage resource was wired Python-side
in PR #1013 ("Prefab stages integration") via
Server/src/services/resources/prefab_stage.py, but its dispatched
`get_prefab_stage` command name was never given a C# handler.
Reading the resource hits CommandRegistry's not-found throw:
Unknown or unsupported command type: get_prefab_stage
This change adds GetPrefabStage at
MCPForUnity/Editor/Resources/Editor/GetPrefabStage.cs, returning the
5 fields the Python PrefabStageResponse pydantic model expects
(isOpen, assetPath, prefabRootName, mode, isDirty) via
PrefabStageUtility.GetCurrentPrefabStage(). Mirrors the EditorState.cs
sibling resource's shape.
No Python-side or schema changes required.
Dan Billeci
4b2b963919