fix: validate priming event in resumability test

Author: felixweinberger

src/server/streamableHttp.test.ts

@@ -1420,8 +1420,10 @@ describe('StreamableHTTPServerTransport with resumability', () => {
         // Read the notification from the SSE stream
         const reader = sseResponse.body?.getReader();
 
-        // Skip the priming event
-        await reader!.read();
+        // Read and validate the priming event
+        const { value: primingValue } = await reader!.read();
+        const primingText = new TextDecoder().decode(primingValue);
+        expect(primingText).toContain('id: ');
 
         const { value } = await reader!.read();
         const text = new TextDecoder().decode(value);