perf(lab): stream sealed spatial playback tracks

src/k1link/perception/geometry.py

@@ -344,6 +344,27 @@ class RecordedGeometryStore:
         points.setflags(write=False)
         return points
 
+    def playback_points_map(self) -> FloatArray:
+        """Expose the sealed contiguous map-point track for binary LAB playback.
+
+        The returned array is the exact source-pack point index space.  It is
+        read-only and deliberately excludes any UI projection or resampling so
+        the browser can retain it once and derive the current increment by the
+        verified offsets below.
+        """
+
+        points = np.asarray(self._source["cloud_points_map"], dtype=np.dtype("<f4"))
+        if not points.flags.c_contiguous:
+            raise GeometryProviderError("source playback point track is not contiguous")
+        points.setflags(write=False)
+        return points
+
+    def playback_point_offsets(self) -> tuple[int, ...]:
+        """Return immutable offsets into :meth:`playback_points_map`."""
+
+        offsets = np.asarray(self._source["cloud_offsets"], dtype=np.int64)
+        return tuple(int(value) for value in offsets)
+
     def point_step_candidates_for_frame(self, frame_index: int) -> UInt8Array | None:
         """Expose the sealed low-step diagnostic in the source point index space.