fix(test-utils): Use server time for listener registration, not client time

The listener was using the client's timestamp from the query param, but
due to network latency, events could be buffered between when the client
generated its timestamp and when the HTTP request reached the server.

Timeline of the bug:
1. Client: T1 = 1000ms (generates timestamp)
2. Client: Sends HTTP request with ?timestamp=1000
3. [NETWORK DELAY]
4. Previous test's event arrives at proxy at T2 = 1002ms (buffered!)
5. Server receives HTTP request at T3 = 1003ms
7. Buffer check: 1002 > 1000 = TRUE → stale event passes!

Fix: Use the server's current time when the listener is actually
registered. This ensures we only receive events that arrived AFTER
the listener was registered on the server.

Author: BYK

dev-packages/test-utils/src/event-proxy-server.ts

@@ -133,11 +133,12 @@ export async function startProxyServer(
     eventCallbackResponse.statusCode = 200;
     eventCallbackResponse.setHeader('connection', 'keep-alive');
 
-    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-    const searchParams = new URL(eventCallbackRequest.url!, 'http://justsomerandombasesothattheurlisparseable.com/')
-      .searchParams;
-    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-    const listenerTimestamp = Number(searchParams.get('timestamp')!);
+    // CRITICAL: Use the SERVER's current time when the listener is actually registered,
+    // NOT the client timestamp from the query param. Due to network latency, events may
+    // have been buffered between when the client generated its timestamp and when the
+    // HTTP request reached this server. Using server time ensures we only get events
+    // that arrived AFTER the listener was actually registered on the server.
+    const listenerTimestamp = getTimestamp();
 
     const callbackListener: EventCallbackListener = {
       callback: (data: string): void => {