For agents, on top of README.md, which they read first.

• Output goes under run/, which is gitignored. Do not write frames anywhere tracked.
• Link's position reads 0 until a save file is loaded and the game is in play; zeros at the title or name-registration screen are correct, not a broken read.
• The snapshot round trip is this crate's test of packages/console. Console has no rust_test of its own; do not remove the assert as noise.