Release v7.51.4

Changed

• Every skill body now stays under the 16,000-character authoring target: tables, extended examples and long procedures in 34 skills (most of the Screenplay skills, the Chronicle clients, reactors, reducers and projections, and the Arc command, query and identity skills) moved into references/, each with a pointer that says when to read it. No guidance was removed. (#686)
• Verification warns when a skill body grows past the 16,000-character target, instead of at 18,000. (#686)
• Verification fails when a relative link in a skill or one of its references does not resolve from the file it is in. (#686)