tests(annotations): guard on the 'dataset' extra so base fast-test tier skips cleanly

Fast Pytest Tests failed at COLLECTION in the base '--extra test' tier
with 'ModuleNotFoundError: No module named datasets': tests/annotations/
conftest.py imported the fixture dataset builder (-> lerobot.datasets ->
the HF 'datasets' lib + pandas/pyarrow), which only ship under the
'dataset' extra, so the whole annotations package crashed.

Fix uses the repo's proven module-level guard pattern (see
tests/datasets/test_language.py), NOT a conftest-level importorskip —
verified empirically that pytest.importorskip raised during conftest
*import* is treated as a collection ERROR (exit 1), while module-level
importorskip is a clean SKIP.

  * conftest.py: import build_annotation_dataset LAZILY inside the
    fixtures so the conftest itself imports cleanly in every tier.
  * test_modules / test_validator / test_writer / test_pipeline_recipe_
    render: add module-level pytest.importorskip('datasets') +
    ('pandas') before the pyarrow / lerobot.* imports (# noqa: E402 to
    match the existing convention). pyarrow-importing modules place the
    guard before the pyarrow import.
  * tests/scripts/test_lerobot_annotate.py: same guard (its _push_to_hub
    path imports lerobot.datasets).

Result:
  - base / hardware / viz tiers (no dataset extra): annotation tests
    skip cleanly; the rest of the suite runs -> exit 0.
  - dataset tier: datasets present -> guards pass through -> annotation
    tests run with the stub VLM. The pipeline modules import only
    stdlib + relative + lerobot.datasets (no module-level datatrove /
    vllm / openai), so they import fine there.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/scripts/test_lerobot_annotate.py

@@ -3,6 +3,13 @@
 import json
 from types import SimpleNamespace
 
+import pytest
+
+# ``lerobot.scripts.lerobot_annotate`` (and the ``_push_to_hub`` path it
+# exercises) imports ``lerobot.datasets``, which only ships under the
+# ``dataset`` extra. Skip in tiers without it instead of erroring.
+pytest.importorskip("datasets", reason="datasets is required (install lerobot[dataset])")
+
 
 def test_push_to_hub_tags_uploaded_dataset_revision(tmp_path, monkeypatch):
     from lerobot.scripts.lerobot_annotate import _push_to_hub