Agent Skills: variation-theory

Apply variation theory of learning to structure content using contrast, generalization, and fusion patterns. Variation must target the critical aspects of the learning objective. Use proactively when (1) writing educational materials, explanations, tutorials, or lecture slides, (2) designing or reviewing examples in documentation, READMEs, or literate programs (.nw files), especially when multiple examples illustrate alternative approaches to the same task, (3) structuring code examples, CLI usage examples, or API examples where the reader should notice what differs between alternatives, (4) user mentions variation theory, learning theory, pedagogy, contrast, invariance, or critical aspects. Also activate when asked to elaborate, make concrete, or add examples to existing content. Works alongside literate-programming and didactic-notes skills; in educational LaTeX or .nw materials, keep variation-analysis labels in \ltnote{} rather than student-facing prose, unless the document itself is about that design.