[kvlonge]

Why

Renaming and moving models and columns is a headline feature, but the docs only covered it in the CLI reference, with migrations buried under Models.

Changes

• New Concepts page, Refactoring, covering model renames and moves, column renames, old-name views, checking impact and refusals, with real 0.138.0 output.
• A Refactoring sidebar group right after Semantic Compilation, holding the new page, Model migrations and Column migrations (slugs unchanged).
• Introduction and quickstart link to it; bundled skill references regenerated.

Verification

• Every sample is real sqb 0.138.0 output on the waffle-shop playground; the site builds and the page renders with the new group.