An RFC 9728 `WWW-Authenticate: Bearer resource_metadata="…"` challenge was
parsed and then dropped by the normalized `AuthChallenge`, so every
challenge-driven `mcpAuth()` call ran discovery without it and probed
locations derived from the MCP server URL instead. OAuth failed outright
against any server whose metadata document lives off the well-known path.
The SDK handles this correctly inside its own transports, but the Inspector
never reaches that path — it intercepts the 401 and drives `auth()` itself
to capture the authorization URL and run the step-up scope union.
Carry the advertised URL on `AuthChallenge` as a string (it crosses the web
client's remote-backend boundary as JSON), convert it at the OAuth boundary,
and pass it to the standard challenge leg, the forced step-up leg, and CIMD
pre-registration — which runs before `auth()` and did its own discovery. A
malformed value is ignored rather than surfaced, matching the SDK's parser.
The callback leg needs nothing: SDK `auth()` persists the URL in its
discovery state.
Adds an `oauth.resourceMetadataPath` test-server mode that moves the
document off the well-known path entirely, so the integration test proves
discovery genuinely fails without the fix.
Closes#2071
Signed-off-by: cliffhall <cliff@futurescale.com>
f8a46726b7