Add mixed_armor source (5635 images / 7634 objects, WebDataset tar)

Uniform label schema (missing fields as null) so the viewer infers one structure; pack.py normalizes

Card: one viewer config per source

Card: only declare the train split until test data exists

Add QDU recordings: qdu_damo, qdu_gimbal_0507, qdu_gimbal_0509; add pack.py

Format spec, sticker registry and export tool

initial commit