Fix: timeout abort reason is TimeoutError

Issue #4021 · PR #4045 · Base: 7f9160f0

Before Fix

four-dev @ 7f9160f0

Timeout and hx-sync:replace both report AbortError.

Click Timeout…

After Fix

7f9160f0 + fix

Timeout uses TimeoutError; replace stays AbortError.

Click Timeout…
Mock fetch() never resolves. Discriminator is ctx.request.signal.reason.name.