mego viewer: dial the main cam a bit smaller for a more balanced grid

mego viewer: bottom-align head_fisheye side tiles to the main cam edge (space-between columns)

mego viewer: bigger centred main cam, compact hand/head-pose panels flush below, spans drop under cams <=1360px

ego viewer: rework 5-view sync — identity-keyed (was leaving head_stereo_left unsynced), playback-rate trim instead of per-frame seeks (kills the judder/loop/freeze on side tiles)

ego viewer: hand-pose 3D no longer blank when paused at t=0 (snap past leading all-zero pose frames)

ego viewer: guard/throttle slave-video sync (fixes head_fisheye_left seek-storm on cold load)

mego viewer: HF download links for dataset files, spans auto-scroll to current step, projection off by default

egoSample: unified scenario-grouped viewer (5 MEgo 5-cam tasks + 6 PICO demos)