Record ADR 0001: the MCP server is an OAuth 2.1 Resource Server that MAY
delegate to an upstream authorization server, and will NOT issue tokens or
act as an Identity Provider. Gives a single citable ruling to decline the
recurring "native authorization server" PRs (e.g. #373).
Also remove the surface signal that invites them: reframe the
OAuthProxyMiddleware class docblock to lead with its delegation intent and
state explicit non-goals (never mints/signs/stores/rotates tokens), and add
a "Scope" section to docs/authorization.md describing the three OAuth roles
and what the SDK does not do.
No behavior change — docblock, docs, and ADR only.
