PLACEHOLDER ARTIFACT — Firsthand sample pack

This file stands in for a real Rerun (.rrd) recording of a sample episode.
Replace it with a genuine recording export before publishing.

Expected contents of the real artifact:
  - /world/head_cam        image stream, 3840x2160 @ 60 fps
  - /world/wrist_cam_left  image stream, 1920x1080 @ 60 fps
  - /world/wrist_cam_right image stream, 1920x1080 @ 60 fps
  - /world/depth           depth image, 848x480 @ 30 fps, metric mm
  - /world/imu             6-DoF, 200 Hz
  - /world/hands/{left,right}/joints   21 x 3, metric
  - /world/body/joints                 24 x 3, metric
  - /world/segments        instance masks with tracked ids
  - /meta/action_segments  verb + noun, frame-accurate
  - /meta/calibration      intrinsics + extrinsics, per-session solve