Drop the success-path `abortRequest: false` change and its regression test:
real browsers (Chrome, Firefox) keep a completed request's xhr through
abort(), so the success path was never affected — that was a jsdom-only
artifact. Remove the throwaway reproduction example.
The fix remains: forward the server response to the `upload-error` event
(and `file.response`), and skip aborting the already-completed request on the
error path so the response is preserved.
9e394eb8f2