migration: reconcile stale meta episode count to data+video files

When the data files and video files agree on episode count N but the metadata
lists a different count, rewrite meta/episodes.jsonl, meta/episodes_stats.jsonl
and info.json to N before the v2.1->v3.0 converter runs (which otherwise raises
'Number of episodes is not the same'). Only the safe direction is handled:
trimming metadata that lists MORE episodes than exist. Non-contiguous data,
data/video disagreement, or metadata missing episodes are left untouched.

community_v3_migration/run_migration.py

@@ -17,7 +17,7 @@ from huggingface_hub import HfApi
 
 import so_arm_frame
 from classify import classify, is_end_effector, load_info
-from fix_dataset import fix_dataset_in_place
+from fix_dataset import fix_dataset_in_place, reconcile_episode_count
 
 SRC_REPO = "HuggingFaceVLA/community_dataset_v3"
 
@@ -171,6 +171,10 @@ def migrate_one(api, dst_repo, sub, work_dir, no_upload) -> dict:
 
     result = fix_dataset_in_place(local)          # SO-arm value fix (or structural_only)
 
+    reconciled = reconcile_episode_count(local)   # align stale meta counts to data+video files
+    if reconciled:
+        result["action"] = f"{result['action']}; {reconciled}"
+
     from lerobot.scripts.convert_dataset_v21_to_v30 import convert_dataset
     convert_dataset(repo_id=sub, root=str(local), push_to_hub=False)  # v2.1 -> v3.0, in place