perf(lab): stream sealed spatial playback tracks

apps/control-station/test/m4ReplayThreat.test.mjs

@@ -10,6 +10,7 @@ let fetchM4ThreatVisual;
 let fetchM4ThreatTimeline;
 let fetchM4ThreatTimelineChunk;
 let fetchM4ThreatCameraPointOverlay;
+let hydrateM4ThreatTimelineFrame;
 let selectM4ThreatTimelineFrame;
 let selectM4ThreatTimelineSequence;
 let advanceRecordedEvidencePlayback;
@@ -33,6 +34,7 @@ before(async () => {
     fetchM4ThreatTimeline,
     fetchM4ThreatTimelineChunk,
     fetchM4ThreatCameraPointOverlay,
+    hydrateM4ThreatTimelineFrame,
     selectM4ThreatTimelineFrame,
     selectM4ThreatTimelineSequence,
   } = await server.ssrLoadModule("/src/core/laboratory/m4ReplayThreat.ts"));
@@ -332,6 +334,45 @@ test("M4.6 timeline keeps only a compact index and decodes bounded spatial chunk
   assert.equal(selectM4ThreatTimelineFrame(chunk.frames, 35.50).sequence, 1);
 });
 
+test("M4.6 hydrates a lightweight timeline frame from one retained binary point track", async () => {
+  const raw = timelineFrame(0, 35.421857292, {
+    body_frame: {
+      origin_map_xyz_m: [10, 20, 30],
+      basis_map_from_body: [[1, 0, 0], [0, 1, 0], [0, 0, 1]],
+    },
+    point_cloud_body_xyz_m: [],
+    point_cloud_source_count: 2,
+    point_cloud_sample_count: 2,
+  });
+  const parsed = await fetchM4ThreatTimelineChunk(resultId, 0, 1, {
+    playbackPointPack: {
+      resultId,
+      frameCount: 4489,
+      pointCount: 2,
+      pointOffsets: new Uint32Array([0, 2, ...Array(4488).fill(2)]),
+      pointsMapXyzM: new Float32Array([11, 20, 30.25, 12, 19.5, 30]),
+    },
+    fetcher: async (input) => {
+      assert.match(String(input), /include_points=false/);
+      return new Response(JSON.stringify({
+        schema_version: "missioncore.recorded-spatial-evidence-chunk/v1",
+        result_id: resultId,
+        start_sequence: 0,
+        frame_count: 1,
+        next_sequence: 1,
+        frames: [raw],
+        authority: "replay-simulated",
+      }), { status: 200 });
+    },
+  });
+  assert.deepEqual(parsed.frames[0].pointCloudBodyXyzM, [
+    [1, 0, 0.25],
+    [2, -0.5, 0],
+  ]);
+  assert.equal(parsed.frames[0].pointCloudSampleCount, 2);
+  assert.equal(typeof hydrateM4ThreatTimelineFrame, "function");
+});
+
 test("M4.8S timeline binds factory-KB4 camera points through its exact endpoint", async () => {
   const replayResultId = `m48s-fixed-class-detector-lab-${"b".repeat(64)}`;
   const endpointRoot = "/api/v1/laboratory/m48s/fixed-class-detector";