feat(convert): integrate process metrics into JSON and SQLite converters

- add process_metrics function to record peak RSS and CPU time
- update JSON converter to include metrics in completion marker
- modify SQLite converter to utilize new metrics for performance tracking
- enhance storage size updates with locking mechanism for concurrent access

convert_json.py

@@ -30,6 +30,7 @@ from common.pipeline import (
 	check_dependencies,
 	load_lab_config,
 	parse_task_args,
+	process_metrics,
 	remove_stale_marker,
 	write_marker,
 )
@@ -265,7 +266,7 @@ def main() -> int:
 			json_root / "hybrid" / "dataset.jsonld",
 		])
 		update_storage_sizes(out_root / "bench", "json", [("full", conv.full_bytes), ("hybrid", hybrid_bytes)])
-		marker_path = write_marker(out_root, TASK_ID, {
+		entries = {
 			"full_files": conv.full_files,
 			"full_bytes": conv.full_bytes,
 			"hybrid_bytes": hybrid_bytes,
@@ -273,7 +274,9 @@ def main() -> int:
 			"tracks": conv.counts["tracks"],
 			"cycle_rows": conv.counts["cycle_rows"],
 			"loop_points": conv.counts["loop_rows"],
-		})
+		}
+		entries.update(process_metrics())
+		marker_path = write_marker(out_root, TASK_ID, entries)
 	except Exception:
 		logger.critical("task %s failed", TASK_ID, exc_info=True)
 		return 1