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

pom.xml

@@ -18,6 +18,7 @@
     <module>adk</module>
     <module>code-review-bot</module>
     <module>agentic-patterns</module>
+    <module>mcp-sdk-plain</module>
   </modules>
 
   <properties>
@@ -34,6 +35,9 @@
     <spring-ai.version>2.0.1</spring-ai.version>
     <onnxruntime.version>1.31.0</onnxruntime.version>
     <spring-boot.version>4.1.1</spring-boot.version>
+    <!-- Verified on Maven Central 2026-11-08 -->
+    <mcp.sdk.version>2.1.0</mcp.sdk.version>
+    <jetty.version>12.1.14</jetty.version>
     <junit.version>6.1.3</junit.version>
     <assertj.version>3.27.6</assertj.version>
     <slf4j.version>2.0.17</slf4j.version>