UI: Fix Monaco workers crashing in production mode (#67546)

`?url` does not run the Vite worker pipeline. For `editor.worker.js` it
inlines the raw source as a base64 data URL (the source is below the
default `assetsInlineLimit`), and the inlined module still has bare
specifier imports it cannot resolve in a Worker context. For
`json.worker.js` it copies a partly-bundled file whose top-level
`import '../../editor/editor.worker.js'` resolves to a path that does
not exist in the build output. Both cases manifest at runtime as
"Could not create web worker(s). Falling back to loading web worker
code in main thread" followed by a stream of fallback fetch errors.

Switch to `?worker&url`: Vite runs the file through the worker pipeline
(bundling all dependencies into a self-contained IIFE) and the URL
query suffix returns the resulting URL as a string instead of a Worker
constructor. The Blob shim from #67352 then imports a properly bundled
worker, restoring real worker-thread execution.

Co-authored-by: Rahul Vats <43964496+vatsrahul1001@users.noreply.github.com>