fix(eval): prevent eval_policy crash when start_seed is None and num_envs>1 (#4203)

* fix(eval): align seed list length with num_envs when unseeded

eval_policy appended a single None per batch to all_seeds on the unseeded path while the reward and success lists grew by num_envs. The per-episode zip(..., strict=True) then raised ValueError for num_envs > 1. Extend all_seeds by num_envs so the lists stay aligned.

* chore(tests): delete lerobot_eval test

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Co-authored-by: Devin Lai <markauto75@gmail.com>

src/lerobot/scripts/lerobot_eval.py

@@ -564,7 +564,7 @@ def eval_policy(
         if seeds:
             all_seeds.extend(seeds)
         else:
-            all_seeds.append(None)
+            all_seeds.extend([None] * env.num_envs)
 
         # FIXME: episode_data is either None or it doesn't exist
         if return_episode_data: