Advance one N&M step-chapter

The connective workflow for moving the book forward one Ontology Development 101 step. It orchestrates the schema edit, the re-freeze, and the prose so they stay consistent — the thing neither CLAUDE.md (the standing conventions) nor the mdbook-listings skill (the tool mechanics) owns by itself.

Read CLAUDE.md first — its "Authoring with mdbook-listings", "freeze foot-gun", and "Conventions" sections are binding and not repeated here.

Step 0 — orient