Merge origin/pr/6 into pr/6 — keep local refactor (openenv, env, no legacy engine)

Merge origin/main into pr/6 — keep pr/6 refactor (openenv, env, no legacy engine)

feat(ui): update Fold3DCanvas, RewardPanel, InfoBadges and rebuild assets

new-environment (#5)

feat(frontend): replay mode, camera angle fix, endpoint alignment

refactor(app): update App and StepFeed for new fold/metrics schema

refactor(metrics): replace reward decomposition with engine metrics

feat(3d): render engine paper_state directly with strain heatmap

fix(canvas): adapt CreaseCanvas to engine FOLD-format paper_state

iana (#1)