perf(lidar): avoid duplicate replay decode during build

src/k1link/compute/lidar_replay.py

@@ -398,12 +398,16 @@ def build_lidar_replay_pack_v2(
             pose_coverage_threshold_ms=pose_coverage_threshold_ms,
         )
         _write_json(staging / LIDAR_QUALITY_REPORT_NAME, quality)
-        equivalence = _equivalence_report(
-            pack_id,
-            logical_sha256,
-            source,
-            arrays,
-        )
+        persisted_arrays = _MaterializedNpz(arrays_path)
+        try:
+            equivalence = _equivalence_report_from_arrays(
+                pack_id,
+                logical_sha256,
+                arrays,
+                persisted_arrays,
+            )
+        finally:
+            persisted_arrays.close()
         _write_json(staging / LIDAR_EQUIVALENCE_REPORT_NAME, equivalence)
         artifacts = [
             _artifact_descriptor("lidar-arrays", arrays_path, "application/x-npz"),
@@ -816,7 +820,22 @@ def _equivalence_report(
     capture_path: Path,
     replay_arrays: Any,
 ) -> dict[str, object]:
-    source_arrays = _capture_arrays(capture_path)
+    return _equivalence_report_from_arrays(
+        pack_id,
+        logical_sha256,
+        _capture_arrays(capture_path),
+        replay_arrays,
+    )
+
+
+def _equivalence_report_from_arrays(
+    pack_id: str,
+    logical_sha256: str,
+    source_arrays: Any,
+    replay_arrays: Any,
+) -> dict[str, object]:
+    """Compare one source-derived array set with its persisted replay image."""
+
     comparisons: dict[str, dict[str, object]] = {}
     mismatch_count = 0
     for name in sorted(_ARRAY_DTYPES):