Scaffold a Lean 4 library project with Mathlib or PFR dependencies, Lake test/lint wiring, GitHub Actions CI, text linting, and agent instructions. Use when the user says "scaffold a Lean library", "new Lean project", "new Mathlib project", "create a Lean formalization repo", "start a Mathlib-downst
Scaffold a Lean 4 library project with Mathlib or PFR dependencies, Lake test/lint wiring, GitHub Actions CI, text linting, and agent instructions. Use when the user says "scaffold a Lean library", "new Lean project", "new Mathlib project", "create a Lean formalization repo", "start a Mathlib-downstream library", or "create a PFR downstream formalization". For Lean proof, naming, or module edits i