401 retry fails for fetch(new Request(...)) with a body (stream consumed) #9

Follow-up surfaced during #6 review.

Problem

Both fetch interceptors (src/nip98-interceptor.js and src/injected.js) retry a failed (401) request using the same url argument they were originally called with. When the page calls fetch(new Request(url, { body: ... })), that Request has a ReadableStream body that is consumed on the first fetch. The retry then receives a Request with an empty/locked body and rejects with a TypeError — the caller sees a rejected fetch instead of the original 401 response.

Scope

• Only affects fetch(new Request(...)) form with a non-empty body.
• Does NOT affect fetch(url, { method, body }) form — that form passes a fresh body on each call.
• Most Solid code uses the second form, which is why this hasn't been observed.

Proposed fix

At the top of the fetch wrapper, if input instanceof Request (or cross-realm equivalent — see #8), clone the Request immediately and keep the clone for potential retry. When retrying, use the clone (or a freshly constructed Request from the clone) so the body stream is fresh.

Consider headers/signal/method propagation during cloning.

Scope note

Not fixing in #6 because that PR is scoped to the auth-overwrite bug. This is a separate correctness issue for a different fetch input shape.