Set Mcp-Protocol-Version in client requests after init, and warn when it doesn't match negotiated version (it SHOULD match)

src/shared/transport.ts

@@ -75,4 +75,11 @@ export interface Transport {
    * The session ID generated for this connection.
    */
   sessionId?: string;
+
+  /**
+   * The protocol version used for the connection.
+   *
+   * Only set after the initialize response was received.
+   */
+  protocolVersion?: string;
 }