Add video playback analytics events (#11629)

src/analytics/metrics/types.ts

@@ -1397,6 +1397,41 @@ export type Events = {
     playlist: string
   }
 
+  /**
+   * The playable video was meaningfully visible. This is an exposure event,
+   * not proof that playback started. Fires once per mounted video item.
+   */
+  'video:impression': {
+    postUri?: string
+    postAuthorDid?: string
+    context: 'embed' | 'immersiveFeed'
+    presentation: 'video' | 'gif'
+  }
+  /**
+   * Playback advanced far enough to render the first frame. Preloading and
+   * merely becoming active do not count. Fires once per mounted video item;
+   * automatic loops do not produce another event.
+   */
+  'video:playback:start': {
+    postUri?: string
+    postAuthorDid?: string
+    context: 'embed' | 'immersiveFeed'
+    presentation: 'video' | 'gif'
+    autoplay: boolean
+  }
+  /**
+   * The user activated a third-party media player. Cross-origin players do
+   * not expose confirmed playback consistently, so this must not be treated
+   * as equivalent to video:playback:start without an explicit methodology.
+   */
+  'externalEmbed:playerActivated': {
+    postUri?: string
+    postAuthorDid?: string
+    source: string
+    playerType: string
+    mediaType: 'video' | 'audio' | 'gif' | 'other'
+  }
+
   // === Video upload funnel (Frontend Spec section D) ===
   // Every event carries uploadId (client-generated UUID, ties one upload
   // session end-to-end) + engine (compression engine id, e.g.