Every corpus file under rules/srd-5.2/ must parse as markdown with YAML frontmatter, carry the universal name/type/source fields, satisfy its kind's extra fields (spell, monster, magic-item; core/class/feat add nothing), and have a filename that matches the deterministic slug of its name with no collisions elsewhere in the layer. This is the schema layer of storied srd verify, the deterministic gate described in plans/0002-srd.md. It does not yet check fidelity against the vendored source, coverage of the vendored tree, or corpus shape (entry counts, README, meta.yaml); those layers land in follow-up commits and this one is not wired into pre-commit or the CLI yet. Adds serde, serde_yaml_ng (a maintained continuation of the now-archived serde_yaml), and regex as dependencies. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_017jBcx24HfGr66ZAJnYf1fR