Add periodic stderr messages.

In everything.ts
- add a 10 second interval for sending 'notifications/stderr' messages to the client

This was created in order to test the display and clearing of stderr messages in the client.
- see https://github.com/modelcontextprotocol/inspector/pull/286

src/everything/everything.ts

@@ -114,8 +114,9 @@ export const createServer = () => {
 
   let subscriptions: Set<string> = new Set();
   let subsUpdateInterval: NodeJS.Timeout | undefined;
-  // Set up update interval for subscribed resources
+  let stdErrUpdateInterval: NodeJS.Timeout | undefined;
 
+  // Set up update interval for subscribed resources
   subsUpdateInterval = setInterval(() => {
     for (const uri of subscriptions) {
       server.notification({
@@ -154,6 +155,19 @@ export const createServer = () => {
       server.notification(message);
   }, 15000);
 
+
+  // Set up update interval for stderr messages
+  stdErrUpdateInterval = setInterval(() => {
+    const shortTimestamp = new Date().toLocaleTimeString([], {
+      hour: '2-digit',
+      minute: '2-digit',
+      second: '2-digit'
+    });    server.notification({
+      method: "notifications/stderr",
+      params: { content: `${shortTimestamp}: A stderr message` },
+    });
+  }, 10000);
+
   // Helper method to request sampling from client
   const requestSampling = async (
     context: string,
@@ -676,6 +690,7 @@ export const createServer = () => {
   const cleanup = async () => {
     if (subsUpdateInterval) clearInterval(subsUpdateInterval);
     if (logsUpdateInterval) clearInterval(logsUpdateInterval);
+    if (stdErrUpdateInterval) clearInterval(stdErrUpdateInterval);
   };
 
   return { server, cleanup };