MCP Will Redesign tools/call and Add Progressive Tool Discovery

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A Core Primitives WG (forming now) will redesign the tools/call interface because allowing both content and structuredContent in one response has confused server and client authors and produced diverging implementations. The same group starts an experimental progressive discovery mechanism so clients learn a server's tools and resources as needed instead of ingesting the whole catalog up front, tied to the caching work in the transport area. Content annotations may be deprecated outright if implementers still do not use them, which would resolve the visibility confusion in SEP-2200.