Add missing isInitialized method to McpSyncClient (#181)

The isInitialized method is present in McpAsyncClient and needs to be
mirrored in McpSyncClient.

Signed-off-by: jitokim <[email protected]>

Author: jitokim

mcp/src/main/java/io/modelcontextprotocol/client/McpSyncClient.java

@@ -97,6 +97,14 @@ public McpSchema.Implementation getServerInfo() {
 		return this.delegate.getServerInfo();
 	}
 
+	/**
+	 * Check if the client-server connection is initialized.
+	 * @return true if the client-server connection is initialized
+	 */
+	public boolean isInitialized() {
+		return this.delegate.isInitialized();
+	}
+
 	/**
 	 * Get the client capabilities that define the supported features and functionality.
 	 * @return The client capabilities