test(ui): проверить ожидание первого сообщения SSE

tests/e2e/live-stream-fixture.ts

@@ -1,9 +1,9 @@
 import type { Page } from '@playwright/test'
 
 // Keep a response open; the browser test controls sample delivery independently of HTTP routes.
-export async function installOpenLiveStream(page: Page, path: string, sample: unknown) {
+export async function installOpenLiveStream(page: Page, path: string, sample: unknown, sendImmediately = true) {
   await page.clock.install()
-  await page.addInitScript(({ path, sample }) => {
+  await page.addInitScript(({ path, sample, sendImmediately }) => {
     const originalFetch = window.fetch.bind(window)
     window.fetch = async (input, init) => {
       const url = new URL(input instanceof Request ? input.url : String(input), location.href)
@@ -18,12 +18,12 @@ export async function installOpenLiveStream(page: Page, path: string, sample: un
           }
           const heartbeat = () => controller.enqueue(encode(': heartbeat\r\n\r\n'))
           Object.assign(window, { sendLiveSample: send, sendLiveHeartbeat: heartbeat })
-          send()
+          if (sendImmediately) send()
         },
       })
       return new Response(stream, { headers: { 'Content-Type': 'text/event-stream' } })
     }
-  }, { path, sample })
+  }, { path, sample, sendImmediately })
 }
 
 export async function resumeLiveStream(page: Page) {