fix(annotate): default frame provider to video keys, not image keys

VideoFrameProvider derived its default camera and camera list from
meta.camera_keys, which mixes image- and video-stored cameras. The
clip/decode paths read videos/<key>/from_timestamp, which only exists
for video keys, so an image-stored camera sorted first (e.g.
observation.images.wrist) crashed the plan phase with a KeyError.

Restrict the list and default to meta.video_keys. Add a regression test
and point the example job at the dataset's actual video camera. Skip
bandit B607 (ffmpeg/git are intentionally resolved via PATH).

Co-authored-by: Cursor <cursoragent@cursor.com>

pyproject.toml

@@ -401,7 +401,7 @@ exclude_dirs = [
     "benchmarks",
     "src/lerobot/datasets/push_dataset_to_hub",
 ]
-skips = ["B101", "B311", "B404", "B603", "B615"]
+skips = ["B101", "B311", "B404", "B603", "B607", "B615"]
 
 [tool.typos]
 default.extend-ignore-re = [