Allow no-reply notifications; also write messages to stderr

Treat a callback returning false as a signal to suppress a JSON-RPC reply (jsonrpc2.extract). Add a special-case in mcploader to return false for "notifications/initialized" so no response is sent. In stdio-server, skip sending falsy messages, keep object serialization, and write outgoing messages to both StdOut and StdErr (useful for logging/debugging). Small cleanup in catch formatting.

lib/jsonrpc2.js

@@ -69,12 +69,15 @@ function extract(message, callback) {
     try {
         var result = callback(data.method, params, id);
         
-        return {
-            jsonrpc: "2.0",
-            result: result === undefined ? null : result,
-            id: id
-        };
+        if (result !== false) {
+            return {
+                jsonrpc: "2.0",
+                result: result === undefined ? null : result,
+                id: id
+            };
+        }
         
+        return result;
     } catch (e) {
         return {
             jsonrpc: "2.0",

lib/stdio-server.js

@@ -16,14 +16,17 @@ function StdioServer() {
     };
     
     this.send = function (message) {
+        if (!message) return;
+        
         if (typeof message === "object") {
             try {
                 var _serialized = JSON.stringify(message);
                 message = _serialized;
-            } catch (e) { /* ignore */ };
+            } catch (e) { /* ignore */ }
         }
         
         WScript.StdOut.WriteLine(message);
+        WScript.StdErr.WriteLine(message);
     };
     
     this.listen = function () {

mcploader.js

@@ -31,6 +31,11 @@ function main(args) {
                     };
                 }
                 
+                if (method === "notifications/initialized") {
+                    // DO NOT return anything
+                    return false;
+                }
+                
                 if (method == "tools/list") {
                     return {
                         "tools": [