Removes pins added while making the auto-default suite pass that weren't
actually testing older-protocol-only behavior, and keeps (with a stated
reason) the ones that are. Along the way, fixes two real defects the audit
surfaced in the modern protocol path: PingMiddleware could leak a
_active_sessions entry when a connection's exit_stack closed before its
keepalive task got its first scheduler turn, and FastMCP(experimental_
capabilities=...) was silently dropped from server/discover responses
(it only ever reached the legacy initialize handshake).
Client negotiates the newest mutual protocol era by default (probe
server/discover, fall back to the initialize handshake). ProxyClient and the
inspect utility explicitly pin the handshake era so proxy forwarding and
server_info reads are unchanged. SSE and multi-server config transports are
legacy-only. extensions= and result_claims= (SEP-2133) are thin passthroughs
to the SDK session.
* Document icon theme support and add round-trip tests
MCP SDK v2 added a `theme` field to `Icon` (light/dark), letting a
server ship complementary icon variants for clients that render in
different UI themes. Document the field on the icons page and cover
it with round-trip tests through the server/client protocol.
* docs: add 4.0.0 version badge to Theme Variants section
* Implement icon support in fastmcp
* Fix icon feature tests
- Update snapshot for ResourceTemplate to include icons field
- Remove OAuth mounting tests (belong to PR #2119, not this feature)
* Update docs
