fix(lab): restore canonical spatial replay

apps/control-station/test/m48ObjectCentricQuality.test.mjs

@@ -18,6 +18,7 @@ let nextM48ObjectId;
 let laboratoryMetricLegendEntries;
 let nearestLaboratoryRecordedClipFrame;
 let laboratoryRecordedClipEndExclusiveNs;
+let laboratoryRecordedClipClockGate;
 let m48SpatialPlaybackWindow;
 let trimM48SpatialPlaybackCache;
 let nextM48CameraVisibility;
@@ -45,6 +46,7 @@ before(async () => {
   ({
     nearestLaboratoryRecordedClipFrame,
     laboratoryRecordedClipEndExclusiveNs,
+    laboratoryRecordedClipClockGate,
   } = await server.ssrLoadModule(
     "/src/components/laboratory/LaboratoryRecordedClipPlayer.tsx",
   ));
@@ -342,6 +344,21 @@ test("shared recorded clip clock selects exact frames and one stable loop bounda
   assert.equal(laboratoryRecordedClipEndExclusiveNs(frames), 1_300_000_000);
 });
 
+test("shared recorded clip rejects stale media callbacks until an explicit seek lands", () => {
+  assert.deepEqual(laboratoryRecordedClipClockGate(1, 123), {
+    accept: false,
+    pendingSequence: 1,
+  });
+  assert.deepEqual(laboratoryRecordedClipClockGate(1, 1), {
+    accept: true,
+    pendingSequence: null,
+  });
+  assert.deepEqual(laboratoryRecordedClipClockGate(null, 124), {
+    accept: true,
+    pendingSequence: null,
+  });
+});
+
 test("M4.8 camera and spatial visibility are independent without an empty viewer", () => {
   assert.equal(nextM48CameraVisibility("camera", true), true);
   assert.equal(nextM48CameraVisibility("3d", true), false);