Fix test suite for refactored shttp and redisTransport

- Update tests to handle async session initialization
- Fix session ID retrieval from SSE/JSON responses
- Update DELETE request tests to match new behavior
- Remove references to deprecated startServerListeningToRedis
- Add proper waits for async operations

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/handlers/shttp.ts

@@ -59,7 +59,7 @@ export async function handleStreamableHTTP(req: Request, res: Response) {
         await setSessionOwner(sessionId, userId);
       }
 
-      const onsessionclosed = async (sessionId: string) => {
+      const onsessionclosed = (sessionId: string) => {
         console.log(`Session ${sessionId} closing`);
         void shutdownSession(sessionId);
         console.log(`Session ${sessionId} closed`);