JS Built-in: RegExp engine · Pull Request #271 · pierrelf.com/we

Implements issue 3mhn3o5n5fm2l — JS Built-in: RegExp engine.

Summary #

Regex engine (regex.rs): From-scratch regex parser and backtracking matcher supporting character classes, quantifiers (greedy/lazy), anchors, capturing/non-capturing/named groups, alternation, backreferences, lookahead, and escape sequences
RegExp built-in: Constructor, prototype methods (test, exec, toString), all flags (g/i/m/s/u/y), lastIndex tracking, named capture groups
Compiler: RegExp literals (/pattern/flags) now compile to RegExp(pattern, flags) calls
String integration: Added match, matchAll, search; updated replace, replaceAll, split to handle RegExp with $-substitution support

25 regex engine unit tests (parser, matcher, flags)
23 VM integration tests (constructor, literals, exec, test, toString, string methods, flags, quantifiers, alternation, lookahead, char classes, backreferences)
All 412 JS tests pass, full workspace tests pass
cargo clippy --workspace -- -D warnings clean
cargo fmt --all --check clean