The default include matched every yaml across the games root, so a
package could absorb a sibling game's defs (e.g. two game#main setups).
Resolve patterns against the package declaration's directory instead;
a leading slash marks a pattern as root-relative.
Parse yaml/json/toml and markdown code blocks into packages, expanding
$variants via typed-csv and collecting parts, surfaces, and setups by
include patterns. Ships zod validation, a vitest config, and 16 tests.