fix(core): a seek during playback lands a playing video on the new time (#4467)

* fix(core): a seek during playback lands a playing video on the new time

* fix(core): the seek fix passes the comment ratchet without a new comment

* fix(core): keep why a pausing seek still lands, folded into the paragraph above

---------

Co-authored-by: Miguel Angel Simon Sierra <miguelangelsisi098@gmail.com>

packages/core/src/runtime/media.test.ts

@@ -1628,6 +1628,25 @@ describe("syncRuntimeMedia", () => {
     expect(clip.el.currentTime).toBe(5);
   });
 
+  // A seek while playing pauses and syncs in one pass, before the video element has paused.
+  it("a seek that pauses mid-playback lands a lagging playing video on the new time", () => {
+    const clip = createMockClip({ start: 3.85, end: 5.6, duration: 1.75 });
+    Object.defineProperty(clip.el, "paused", { value: false, writable: true });
+    Object.defineProperty(clip.el, "currentTime", { value: 0.031, writable: true });
+    syncRuntimeMedia({ clips: [clip], timeSeconds: 4.109, playing: true, playbackRate: 1 });
+    expect(clip.el.currentTime).toBe(0.031);
+
+    syncRuntimeMedia({
+      clips: [clip],
+      timeSeconds: 4.4,
+      playing: false,
+      playbackRate: 1,
+      forceSync: true,
+    });
+    expect(clip.el.currentTime).toBeCloseTo(0.55, 5);
+    expect(clip.el.pause).toHaveBeenCalled();
+  });
+
   it("mutes when either outputMuted OR userMuted is true (OR invariant)", () => {
     // Explicit validation of the combined-flag contract: setting one to
     // false while the other is true must keep the element muted.

packages/core/src/runtime/media.ts

@@ -461,13 +461,12 @@ export function syncRuntimeMedia(params: {
         (el.ended && canSeekEndedMediaBackward && drift > 0.001) ||
         staleAudioOnFirstTick ||
         (drift > 0.5 && (firstTickOfClip || offsetJumped || catastrophicDrift));
-      // Playing video elements use the browser's native decoder pipeline for
-      // timing. Seeking a playing video resets the decoder, causing a ~150ms
-      // freeze while it re-buffers — during which the monotonic clock advances,
-      // creating a perpetual seek→freeze→drift→seek stutter loop. Skip strict
-      // and force sync for playing videos; only hard sync (>0.5s) warrants
-      // the decoder-reset cost.
-      const isPlayingVideo = el.tagName === "VIDEO" && !el.paused;
+      // Playing videos use the browser's decoder for timing. Seeking one resets the decoder: a
+      // ~150ms freeze while it re-buffers, as the monotonic clock advances, which loops into a
+      // seek→freeze→drift→seek stutter. So a playing video skips strict and force sync; only hard
+      // sync (>0.5s) warrants the decoder-reset cost. A paused transport pauses this video below,
+      // so a seek that pauses mid-playback still lands it.
+      const isPlayingVideo = el.tagName === "VIDEO" && !el.paused && params.playing;
       // Only apply strict sync when offset has stabilized (not growing).
       // During initial buffering, offset grows ~16ms/tick as the timeline
       // advances while media stays at 0. Accumulated drift from pause/play