CMMS embedding: AI Assistant editor-buffer bridge

App.tsx gains a postMessage listener (gated on window.CMMS_SCAD_CONFIG) that
answers 'cmms-ai-editor-get-buffer' with model.source and applies an
'cmms-ai-editor-apply' rewrite via model.source = new_source. Lets the CMMS
AI Assistant read and rewrite the live editor buffer. Standalone use is
untouched.

src/components/App.tsx

@@ -37,6 +37,28 @@ export function App({initialState, statePersister, fs}: {initialState: State, st
     };
   }, []);
 
+  // CMMS AI Assistant editor-buffer bridge (patch, not upstream). Gated on
+  // window.CMMS_SCAD_CONFIG so standalone use is untouched. The embedded chat
+  // (injected by public/vendor/openscad-playground/edit.php) postMessages the
+  // parent window for the current source before each turn and pushes an AI
+  // rewrite back the same way. No dep array: `model` is recreated every render,
+  // so the listener is re-bound each time to keep model.source current.
+  useEffect(() => {
+    if (!(window as any).CMMS_SCAD_CONFIG) return;
+    const onMessage = (event: MessageEvent) => {
+      if (event.origin !== window.location.origin || !event.data || typeof event.data !== 'object') return;
+      const data = event.data as any;
+      if (data.type === 'cmms-ai-editor-get-buffer') {
+        const source = event.source as WindowProxy | null;
+        source?.postMessage({ type: 'cmms-ai-editor-buffer', buffer: model.source }, window.location.origin);
+      } else if (data.type === 'cmms-ai-editor-apply' && data.editor === 'scad' && typeof data.new_source === 'string') {
+        model.source = data.new_source;
+      }
+    };
+    window.addEventListener('message', onMessage);
+    return () => window.removeEventListener('message', onMessage);
+  });
+
   const zIndexOfPanelsDependingOnFocus = {
     editor: {
       editor: 3,