Add mcp-sdk-plain module: MCP server on the plain Java SDK 2.1.0 over stdio and Streamable HTTP, fat jar, wire transcripts and a Spring AI client

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ic4b5oh78z7gcH6QkxafF

mcp-sdk-plain/output/03-http-wire.txt

@@ -0,0 +1,19 @@
+-- POST initialize, Accept: application/json, text/event-stream
+status 200
+content-type application/json;charset=utf-8
+mcp-session-id present: true
+body: {"jsonrpc":"2.0","id":1,"result":{"protocolVersion":"2025-06-18","capabilities":{"logging":{},"resources":{"subscribe":false,"listChanged":true},"tools":{"listChanged":true}},"serverInfo":{"name":"notes-server","version":"1.0.0"},"instructions":"Tools: word_stats, divide, explode. Resources: notes://readme and notes://{name}."}}
+-- POST tools/list without the Mcp-Session-Id header
+status 400
+jsonRpcError: {"code":-32601,"message":"Session ID required in mcp-session-id header"}
+body also contains a Java stackTrace: true
+-- POST initialize with Accept: application/json only
+status 400
+jsonRpcError: {"code":-32601,"message":"text/event-stream required in Accept header"}
+body also contains a Java stackTrace: true
+-- DELETE with the session id ends the session
+status 200
+-- POST tools/list on the ended session
+status 404
+jsonRpcError: {"code":-32603,"message":"Session not found: <session-id>"}
+body also contains a Java stackTrace: true