feat(ci): extract task descriptions and embed in metrics artifact

- Add scripts/ci/extract_task_descriptions.py: runs inside the benchmark
  Docker container (LIBERO/MetaWorld installed) after lerobot-eval and
  writes task_descriptions.json mapping task keys to NL instructions.
  LIBERO: uses libero.libero.benchmark to get suite.get_task(i).language.
  MetaWorld: formats task name as human-readable label.
- Call extraction at the end of each eval bash-c (|| true so never fatal).
- parse_eval_metrics.py reads task_descriptions.json and includes it in
  metrics.json so the health dashboard Space can label videos by task.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/ci/extract_task_descriptions.py

@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+# Copyright 2025 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Extract natural-language task descriptions for a benchmark suite.
+
+Runs inside the benchmark Docker container (where the env library is installed)
+immediately after lerobot-eval, writing a JSON file that parse_eval_metrics.py
+picks up and embeds in metrics.json.
+
+Output format: {"<suite>_<task_idx>": "<nl instruction>", ...}
+
+Usage:
+    python scripts/ci/extract_task_descriptions.py \\
+        --env libero --task libero_spatial \\
+        --output /tmp/eval-artifacts/task_descriptions.json
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import sys
+from pathlib import Path
+
+
+def _libero_descriptions(task_suite: str) -> dict[str, str]:
+    from libero.libero import benchmark  # type: ignore[import-untyped]
+
+    suite_dict = benchmark.get_benchmark_dict()
+    if task_suite not in suite_dict:
+        print(
+            f"[extract_task_descriptions] Unknown LIBERO suite '{task_suite}'. "
+            f"Available: {list(suite_dict.keys())}",
+            file=sys.stderr,
+        )
+        return {}
+    suite = suite_dict[task_suite]()
+    return {f"{task_suite}_{i}": suite.get_task(i).language for i in range(suite.n_tasks)}
+
+
+def _metaworld_descriptions(task_name: str) -> dict[str, str]:
+    # MetaWorld tasks don't expose a separate NL description attribute;
+    # use a cleaned version of the task name as the description.
+    label = task_name.removeprefix("metaworld-").replace("-", " ").strip()
+    return {f"{task_name}_0": label}
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--env", required=True, help="Environment family (libero, metaworld, ...)")
+    parser.add_argument("--task", required=True, help="Task/suite name (e.g. libero_spatial)")
+    parser.add_argument("--output", required=True, help="Path to write task_descriptions.json")
+    args = parser.parse_args()
+
+    descriptions: dict[str, str] = {}
+    try:
+        if args.env == "libero":
+            descriptions = _libero_descriptions(args.task)
+        elif args.env == "metaworld":
+            descriptions = _metaworld_descriptions(args.task)
+        else:
+            print(
+                f"[extract_task_descriptions] No description extractor for env '{args.env}'.",
+                file=sys.stderr,
+            )
+    except Exception as exc:
+        print(f"[extract_task_descriptions] Warning: {exc}", file=sys.stderr)
+
+    out_path = Path(args.output)
+    out_path.parent.mkdir(parents=True, exist_ok=True)
+    out_path.write_text(json.dumps(descriptions, indent=2))
+    print(f"[extract_task_descriptions] {len(descriptions)} descriptions → {out_path}")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())

scripts/ci/parse_eval_metrics.py

@@ -95,6 +95,17 @@ def main() -> int:
             file=sys.stderr,
         )
 
+    task_descriptions: dict[str, str] = {}
+    task_desc_path = artifacts_dir / "task_descriptions.json"
+    if task_desc_path.exists():
+        try:
+            task_descriptions = json.loads(task_desc_path.read_text())
+        except json.JSONDecodeError as exc:
+            print(
+                f"[parse_eval_metrics] Warning: could not parse task_descriptions.json: {exc}",
+                file=sys.stderr,
+            )
+
     metrics = {
         "env": args.env,
         "task": args.task,
@@ -103,6 +114,7 @@ def main() -> int:
         "n_episodes": n_episodes,
         "avg_sum_reward": avg_sum_reward,
         "eval_s": eval_s,
+        "task_descriptions": task_descriptions,
     }
 
     out_path = artifacts_dir / "metrics.json"