pub fn parse_frontmatter(raw: &str) -> (Option<ArtifactMetadata>, Vec<Issue>)Expand description
Parse and schema-validate raw frontmatter YAML.
Returns (metadata, issues): metadata is None only on envelope-level
failures (oversize, malformed YAML, alias, depth, duplicate key,
non-mapping top level); field-level problems always return a constructed
metadata. Issue order is pinned: unknown fields (document order), then
schema_version, id, type, relationships, tags.