Migrate To Rstest

Handles the mechanical work of moving Jest or Vitest test suites over to Rstest without breaking your coverage or test intent. It follows a strict smallest-change-first policy: config and tooling fixes before rewriting tests, and it never touches your production code unless you ask. The skill enforces literal API substitution at every call site (no global shims), preserves legacy configs until each scope goes green, and blocks itself from making sweeping changes without showing you the options first. Useful when you want the migration done methodically rather than in one risky rewrite, especially in monorepos where you're moving packages over incrementally.