SpriteForge agent discipline

Never open files in build/, assets/**/*.png, or .sfcache/.
Never list directories containing thousands of files; use sf list.
Check generated results only with sf validate and sf ascii.
When debugging a backend, first run one asset with --dry-run.
SpriteForge is standalone. Never import game code or hardcode game entity names.
YAML manifests in consuming projects are the only project-specific source of truth.