v0.21.0

Added

• Support capability extensions per SEP-2133 (#405)
• Add range validation for MCP::Annotations#priority per MCP specification (#410)
• Isolate stateless requests in ephemeral sessions per SEP-2567 (#415)

Changed

• Set OIDC application_type on Dynamic Client Registration per SEP-837 (#408)
• Fall back to legacy 2025-03-26 OAuth discovery for servers without PRM (#414)