docs: add 30s dance section + AMP-vs-PPO note

docs: drop unrelated LeIsaac link (this repo is motion-tracking, not manipulation)

fix: correct dataset slugs (lvhaidong/LAFAN1 + ember-lab/LAFAN-G1) + LeIsaac description

docs: drop fake self-citation, keep real upstream papers (DeepMimic + LAFAN)

Initial release: 4 LAFAN motion policies (fight/run/dance/jumps) + textured USD + demo videos