Markdown body-text check types validate relationships between frontmatter metadata and markdown body content.

Check types in this family:

• Code fence language required: Require that opening fenced code blocks include a language tag.
• No heading level jumps: Disallow jumps larger than one heading level (for example H1 -> H3).
• Required section: Require that a heading with specific text exists somewhere in the body.
• Requires H1: Require at least one H1 heading in the markdown body.
• Single H1: Require that the markdown body contains at most one H1 heading.
• Title matches H1: Require a frontmatter field to match the first H1 heading in the body.
• Writing tells: Warn on likely AI-writing tells (em dashes, decorative emoji, overused words, stock phrases) for human review.