Check every link reference definition, decode destinations per CommonMark,
report correct lines for empty headings, autolinks and nested definitions,
reject symlinked record directories and wrong-case path components, and
refuse titles that cannot pass. Only top-level headings count (spec section 6).
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Clarify null scalars, marker handling in frontmatter, the Decision Outcome
prose rule, section extent wording and link rule scope.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>