fix: use randomUUID for priming event fallback ID

Author: felixweinberger

src/server/streamableHttp.ts

@@ -263,9 +263,7 @@ export class StreamableHTTPServerTransport implements Transport {
      * This primes the client's Last-Event-ID for reconnection.
      */
     private async _writePrimingEvent(res: ServerResponse, streamId: string): Promise<void> {
-        const primingEventId = this._eventStore
-            ? await this._eventStore.storeEvent(streamId, {} as JSONRPCMessage)
-            : `priming-${Date.now()}`;
+        const primingEventId = this._eventStore ? await this._eventStore.storeEvent(streamId, {} as JSONRPCMessage) : randomUUID();
 
         let primingEvent = `id: ${primingEventId}\ndata: \n\n`;
         if (this._retryInterval !== undefined) {