Partial requests without X-RSC-Router-Client-Path match a cross-origin Referer's pathname as the navigation source #1005

Low priority. The router's own client always sends X-RSC-Router-Client-Path, so this only affects partial requests made without it.

Problem

When a partial request carries no X-RSC-Router-Client-Path, the navigation source falls back to the Referer header:

• getNavigationContextHeader, src/router/navigation-snapshot.ts:42-46;
• resolveNavigation builds prevUrl = new URL(previousUrl, url.origin) (:97), then matches prevUrl.pathname against this router's table (:111).

An absolute cross-origin Referer keeps its foreign origin, but only its pathname is matched. For example, https://other.example/product/42 is matched as /product/42 on this app. The source route, its params and its name then come from a page the visitor was never on. That source drives:

• the segment diff (which segments are treated as already on the client);
• intercept selection;
• intercept when's from, which gains from.params in the client-when PR.

Expected

Ignore a Referer whose origin differs from the request's. Treat it as no navigation context, the same as a missing header. Alternatively, drop the Referer fallback entirely if no supported client relies on it.

Notes

Not reproduced end to end. The behavior follows from the code above. Found during review of the client-when PR.