chore(dependencies): Update MCP SDK version to 0.12.1 in pom.xml and documentation

Author: codeboyzhou

README.md

@@ -141,7 +141,7 @@ Now it's all set, run your MCP server, choose one MCP client you like and start
 Add the following Maven dependency to your project:
 
 ```xml
-<!-- Internally relies on native MCP Java SDK 0.11.3 -->
+<!-- Internally relies on native MCP Java SDK 0.12.1 -->
 <dependency>
     <groupId>io.github.codeboyzhou</groupId>
     <artifactId>mcp-declarative-java-sdk</artifactId>

docs/docs/getting-started.md

@@ -14,7 +14,7 @@ hide:
 Add the following Maven dependency to your project:
 
 ```xml
-<!-- Internally relies on native MCP Java SDK 0.11.3 -->
+<!-- Internally relies on native MCP Java SDK 0.12.1 -->
 <dependency>
     <groupId>io.github.codeboyzhou</groupId>
     <artifactId>mcp-declarative-java-sdk</artifactId>

pom.xml

@@ -60,7 +60,7 @@
         <jetty.version>12.1.0</jetty.version>
         <junit5.version>5.13.4</junit5.version>
         <logback.version>1.5.18</logback.version>
-        <mcp-sdk.version>0.11.3</mcp-sdk.version>
+        <mcp-sdk.version>0.12.1</mcp-sdk.version>
         <mockito.version>5.19.0</mockito.version>
         <reflections.version>0.10.2</reflections.version>
     </properties>

src/main/java/com/github/codeboyzhou/mcp/declarative/server/McpStreamableServerInfo.java

@@ -1,5 +1,6 @@
 package com.github.codeboyzhou.mcp.declarative.server;
 
+import io.modelcontextprotocol.common.McpTransportContext;
 import io.modelcontextprotocol.server.McpTransportContextExtractor;
 import jakarta.servlet.http.HttpServletRequest;
 import java.time.Duration;
@@ -58,7 +59,7 @@ public static class Builder extends McpServerInfo.Builder<McpStreamableServerInf
     private boolean disallowDelete = false;
 
     private McpTransportContextExtractor<HttpServletRequest> contextExtractor =
-        (request, context) -> context;
+        request -> McpTransportContext.EMPTY;
 
     private Duration keepAliveInterval;