fix(file-viewer): revoke blob URL created by an aborted media load

If the file switches while the fetch/PDF-validation is awaiting, the effect
cleanup runs before objectUrl is assigned, so it revokes nothing and the
in-flight load then creates a blob URL that is never freed. Check
controller.signal.aborted right after createObjectURL and revoke + bail so
rapid switching can't leak object URLs (CodeRabbit: Stability, Major).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/code-editor/view/subcomponents/CodeEditorMediaPreview.tsx

@@ -103,6 +103,16 @@ export default function CodeEditorMediaPreview({
 
         const typed = outType && outType !== blob.type ? new Blob([blob], { type: outType }) : blob;
         objectUrl = URL.createObjectURL(typed);
+
+        // The cleanup may have already run (deps changed during an await), in
+        // which case it revoked nothing because objectUrl was still null. Don't
+        // publish a URL the cleanup will never revoke — drop it ourselves.
+        if (controller.signal.aborted) {
+          URL.revokeObjectURL(objectUrl);
+          objectUrl = null;
+          return;
+        }
+
         setUrl(objectUrl);
         setLoadedKey(sourceKey);
       } catch (loadError: unknown) {