MCP Rust SDK stops treating a pointer found in a guessed .well-known response as an advertised resource.

PR #1264 reclassifies a resource_metadata pointer found in a .well-known candidate's 401 response from Advertised to WellKnownGuess (GitHub). It was being fetched as Advertised, meaning one bad document could end discovery before remaining candidates were tried. A guess only rules itself out, while an advertised URL reports the error, so misclassifying a guess turns a soft miss into a hard discovery failure.