Drop the archived old/ tree, root AI notes, splashgame.md (Arcade lives
in the private sandbox), widgets-dll leftovers, and LAN/oracle helper
scripts. Move download_*.sh into tools/, and move sim/math out of
libs/game/ so the public repo no longer has a game/ directory.
Also quiet first-party compile noise and skip asset-ui tests that need
sandbox kits or uncommitted fixtures.
