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/scripts/raw-stdio.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+# Talks to the fat jar the way Claude Desktop does: newline-delimited JSON-RPC on stdin, responses on stdout.
+# Usage: scripts/raw-stdio.sh   (run `mvn -pl mcp-sdk-plain package` first)
+set -eu
+cd "$(dirname "$0")/.."
+OUT=output/05-fat-jar-raw-stdio.txt
+{
+  echo '$ printf <3 JSON-RPC lines> | java -jar target/mcp-sdk-plain.jar stdio'
+  (
+    printf '%s\n' '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"raw","version":"0"}}}'
+    printf '%s\n' '{"jsonrpc":"2.0","method":"notifications/initialized"}'
+    printf '%s\n' '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"word_stats","arguments":{"text":"one two three"}}}'
+    sleep 3
+  ) | java -jar target/mcp-sdk-plain.jar stdio 2>/dev/null
+} > "$OUT"
+cat "$OUT"