modernize

What problem does it solve? Codebases accumulate legacy TypeScript constructs that newer compiler versions already support replacing, but manually tracking which features apply to your project's exact TypeScript and Node.js versions is tedious and error-prone. ## Core Features & Use Cases - Version-gated feature detection: Reads the project's TypeScript version, Node.js engine, and tsconfig target/module/lib to determine exactly which modern features from the catalog (TS 5.0 through 6.0) are safe to apply. - Pattern-based transforms: Scans target files with grep-compatible detection patterns from versioned example files, applies before/after transforms, and respects documented edge cases where transforms must not run. - Verified application with dry-run: Supports --dry-run previews, then applies edits file-by-file and validates with npx tsc --noEmit and the project test suite, reverting any transform that fails verification. - Use Case: Point it at a legacy src/ directory on a TypeScript 5.5 project and it replaces manual reduce grouping with Object.groupBy, spread-then-sort with toSorted(), and explicit type predicates with inferred ones — all verified by the type checker. ## Quick Start Ask the agent to modernize the src directory with the modernize skill, optionally adding --dry-run to preview proposed changes first.