fix: format stdio test with prettier and add changeset

Author: kai-agent-free

.changeset/fix-stdio-epipe.md

@@ -0,0 +1,5 @@
+---
+'@modelcontextprotocol/server': patch
+---
+
+Handle EPIPE errors gracefully in stdio transport to prevent crashes when the connected process terminates unexpectedly.

packages/server/test/server/stdio.test.ts

@@ -143,7 +143,7 @@ test('should forward non-EPIPE stdout errors to onerror', async () => {
     const server = new StdioServerTransport(input, output);
 
     let reportedError: Error | undefined;
-    server.onerror = (error) => {
+    server.onerror = error => {
         reportedError = error;
     };