Fix undo/redo history affecting multiple files after switching in CodeMirror.

Author: swk777

packages/web/src/components/apps/editor.tsx

@@ -25,7 +25,7 @@ export function CodeEditor({
   const extensions = languageExtension ? [languageExtension] : [];
 
   return (
-    <CodeMirror value={source} theme={codeTheme} extensions={extensions} onChange={onChange} />
+    <CodeMirror key={path} value={source} theme={codeTheme} extensions={extensions} onChange={onChange} />
   );
 }