Upgrade to the 07-28-2026 mcp spec

[jcarver989]

The MCP spec is about to undergo a large revision, see https://blog.modelcontextprotocol.io/posts/sdk-betas-2026-07-28/ and https://blog.modelcontextprotocol.io/posts/2026-07-28-release-candidate/

We'll want to:

1. Upgrade to the latest rmcp
2. Address any breaking changes
3. Refactor to take advantage of the new additions