Named capture groups compile end to end

- The pattern fence lifts: the vendored engine already executes named groups and named backreferences
- Match results project .groups at compile time as the checker's own record shape, with Node's key order, undefined-when-none, and null-read error texts
- Replace and replaceAll resolve $<name> templates with Node's exact edge behaviors; matchAll rows carry groups through for-of, drains, and destructuring
- Destructuring over index-signature records reads through the overflow map generally