feat: add project plugin management (#501)

packages/mcp/src/bridge/scene-bridge.test.ts

@@ -432,6 +432,21 @@ describe('SceneBridge', () => {
       expect(Object.keys(bridge.getNodes()).length).toBe(Object.keys(snap.nodes).length)
     })
 
+    test('loadJSON preserves explicit plugin installs', () => {
+      const snap = bridge.exportJSON()
+      bridge.loadJSON({ ...snap, installedPlugins: ['pascal:trees'] })
+
+      expect(bridge.exportJSON().installedPlugins).toEqual(['pascal:trees'])
+    })
+
+    test('legacy graphs do not become explicitly uninstalled on export', () => {
+      const snap = bridge.exportJSON()
+      const { installedPlugins: _installedPlugins, ...legacy } = snap
+      bridge.loadJSON(legacy)
+
+      expect(Object.hasOwn(bridge.exportJSON(), 'installedPlugins')).toBe(false)
+    })
+
     test('loadJSON throws on malformed JSON string', () => {
       expect(() => bridge.loadJSON('not json')).toThrow(/invalid JSON/)
     })

packages/mcp/src/bridge/scene-bridge.ts

@@ -72,6 +72,9 @@ export class SceneBridge {
         nodes: state.nodes,
         rootNodeIds: state.rootNodeIds,
         collections: state.collections ?? {},
+        ...(state.hasExplicitPluginInstallState || state.installedPlugins.length > 0
+          ? { installedPlugins: state.installedPlugins }
+          : {}),
       }),
     )
   }
@@ -117,6 +120,12 @@ export class SceneBridge {
     }
 
     this.setScene(nodes as Record<AnyNodeId, AnyNode>, rootNodeIds as AnyNodeId[])
+    if (Array.isArray(obj.installedPlugins)) {
+      useScene.getState().setInstalledPlugins(
+        obj.installedPlugins.filter((id): id is string => typeof id === 'string'),
+        { explicit: true },
+      )
+    }
   }
 
   /** Read a single node, or `null` if not present. */

packages/mcp/src/operations/scene-operations.ts

@@ -150,6 +150,7 @@ class SceneOperationsFacade implements SceneOperations {
       nodes: exported.nodes,
       rootNodeIds: exported.rootNodeIds,
       collections: exported.collections as SceneGraph['collections'],
+      installedPlugins: exported.installedPlugins,
     }
   }