feat(auth): per-server authorization and token URL overrides

Adds two optional per-server fields — `oauth.authorizationUrl` and
`oauth.tokenUrl` — that override the endpoints authorization-server
metadata discovery resolved, so a server can be pointed at a development
or staging authorization server without changing what it advertises.

SDK v2 routes both endpoints through the discovered metadata document and
neither through OAuthClientProvider, so the override is applied by
wrapping the client's base fetch and patching the metadata document in
flight (core/auth/endpointOverrides.ts). Wrapping the base fetch — rather
than only the auth fetch — also covers the discovery the SDK runs from
inside the transport on the 401/refresh path.

The fields round-trip through mcp.json, the /api/servers routes, the
runner (CLI/TUI), and the Server Settings → Authorization panel, where a
value that is not an absolute http(s) URL is flagged inline; at runtime
such a value is dropped with a single warning rather than failing the
connection.

Signed-off-by: cliffhall <cliff@futurescale.com>

docs/mcp-server-configuration.md

@@ -175,10 +175,14 @@ These have no analog in the broader `mcp.json` ecosystem. Each is **omitted on w
 | `paginatedLists`                       | `false`    | Fetch tools/resources/prompts one page at a time instead of auto-aggregating                        |
 | `advertisedExtensions`                 | —          | Per-extension overrides for what the Inspector declares in `capabilities.extensions`                |
 | `maxFetchRequests`                     | `1000`     | Network-log retention for this server (`DEFAULT_MAX_FETCH_REQUESTS`); `0` means unlimited           |
-| `oauth`                                | —          | `{ clientId, clientSecret, scopes, authorizationParams, enterpriseManaged, onInsufficientScope }`   |
+| `oauth`                                | —          | `{ clientId, clientSecret, scopes, authorizationParams, authorizationUrl, tokenUrl, enterpriseManaged, onInsufficientScope }` |
 
 `oauth.authorizationParams` is a string→string record of extra query parameters merged into the OAuth **authorization request** URL only — never the token request. Use it for provider-specific hints the core specs don't standardize (Keycloak's `kc_idp_hint`, OIDC's `login_hint` / `prompt` / `acr_values`, Auth0's `audience`). The protocol-critical parameters — `client_id`, `code_challenge`, `code_challenge_method`, `redirect_uri`, `resource`, `response_type`, `scope`, `state` — are **reserved**: the web form rejects them inline, and any that reach the merge anyway are dropped with a warning rather than overriding what the flow set (overriding them breaks PKCE, the CSRF state binding, or RFC 8707). Edit them in Server Settings → Authorization ("Additional authorization parameters"), beside Scopes.
 
+`oauth.authorizationUrl` and `oauth.tokenUrl` override the `authorization_endpoint` and `token_endpoint` that authorization-server metadata discovery resolved. The Inspector deliberately has no such fields by default — it resolves both from the AS's metadata document, exactly as a real MCP host does — but a server under development often advertises its *production* authorization server while you want to hit staging. Set either (they are independent) to an absolute `http(s)` URL and it replaces what the metadata returned, for both the authorization request and the token request; leave blank to use discovery. A malformed value is flagged inline in the form and dropped with a warning at connect time rather than failing the connection. Edit them in Server Settings → Authorization ("Authorization URL override" / "Token URL override").
+
+> Because the override is applied to the *discovered metadata document*, a server whose authorization server publishes no metadata at all is unaffected — there the SDK falls back to `/authorize` and `/token` on the AS origin, and there is nothing to override.
+
 A catalog carrying these fields:
 
 ```json