[Kehrlann]

Adds in-memory tool, prompt and resource repositories (sync and async) for the 2026-07-28 server, adapted from Spring AI. They support pagination, change notifications and resource templates.

var tools = InMemorySyncToolRepository.builder()
    .tool(McpSyncTool.of(tool, (ctx, req) -> ...))
    .changeBroadcaster(broadcaster)
    .build();

The conformance server and most test repositories now use them.

First stab at #1200 , users don't need to implement a repo anymore.