fix(ui): распознавать CRLF и комментарии в потоке SSE

tests/e2e/live-stream-fixture.ts

@@ -10,8 +10,14 @@ export async function installOpenLiveStream(page: Page, path: string, sample: un
       if (url.pathname !== path) return originalFetch(input, init)
       const stream = new ReadableStream<Uint8Array>({
         start(controller) {
-          const send = () => controller.enqueue(new TextEncoder().encode('event: sample\ndata: ' + JSON.stringify(sample) + '\n\n'))
-          Object.assign(window, { sendLiveSample: send })
+          const encode = (value: string) => new TextEncoder().encode(value)
+          const send = () => {
+            // A comment may precede an event; CRLF delimiters may cross chunks.
+            controller.enqueue(encode(': heartbeat\r\nevent: sample\r\ndata: ' + JSON.stringify(sample) + '\r\n\r'))
+            controller.enqueue(encode('\n'))
+          }
+          const heartbeat = () => controller.enqueue(encode(': heartbeat\r\n\r\n'))
+          Object.assign(window, { sendLiveSample: send, sendLiveHeartbeat: heartbeat })
           send()
         },
       })
@@ -23,3 +29,7 @@ export async function installOpenLiveStream(page: Page, path: string, sample: un
 export async function resumeLiveStream(page: Page) {
   await page.evaluate(() => (window as unknown as { sendLiveSample: () => void }).sendLiveSample())
 }
+
+export async function sendLiveHeartbeat(page: Page) {
+  await page.evaluate(() => (window as unknown as { sendLiveHeartbeat: () => void }).sendLiveHeartbeat())
+}