Update difficulty table metadata paths (sub)

sub/difficulty_table.json

@@ -1,8 +1,8 @@
 {
   "meta": {
-    "source_selection": "/home/jiarong/VisExpert/data/visexpert_selection__home_jiarong_VisExpert_output_physics_prediction_20251228_215227_gpt-5_threejs.json",
+    "source_selection": "/home/jiarong/VisPhyWorld/data/visexpert_selection__dataset_sub_half__physics_prediction_20251228_215227_gpt-5_threejs.json",
     "dataset_dir": "/home/jiarong/VisPhyWorld/data/dataset_sub",
-    "detection_dir": "/home/jiarong/VisPhyWorld/data/detection_json_512_sub",
+    "detection_dir": "/home/jiarong/VisPhyWorld/data/detection_json_sub",
     "strategy": "half_per_class_round_robin_by_prefix",
     "counts": {
       "easy": 114,
@@ -12,7 +12,7 @@
     "total": 209,
     "labeled": 209,
     "remaining": 0,
-    "exported_at": "2026-02-06T00:58:36.115387-05:00",
+    "exported_at": "2026-02-08T17:19:05.648370-05:00",
     "language": "en",
     "added_3d_samples_count": 18,
     "added_3d_samples_default_difficulty": "easy"