fix(regex): keep escaped hyphen \- literal inside a character class (#4425)

[proggeramlug]

Summary

Fixes #4425. An escaped hyphen \- inside a JS character class is always a literal hyphen, but Perry's regex translator emitted a bare - for it via push_escaped_literal. The Rust regex crate then read a - flanked by members as a range operator, so [a\- ] translated to the invalid range [a- ] (a 0x61 → space 0x20) and new RegExp threw invalid pattern.

[\-] (sole member) worked because there was nothing to form a range with; [a-z] worked because it's a valid range. Only \- flanked by other members hit the bug.

Fix

In js_regex_to_rust (crates/perry-runtime/src/regex/grammar.rs), when inside a character class, preserve the escape for \- so it stays a literal hyphen regardless of position. Outside a class a hyphen carries no range meaning, so it's still emitted bare.

Verification

The issue's repro now reports OK for every pattern, including marked's GFM table-delimiter regex:

OK   /[\-]/
OK   /[a\- ]/
OK   /[a-z]/
OK   /[:]/
OK   /[ ]/
OK   /[a-z ]/
OK   /[:\- ]/
OK   / {0,3}\|?(?:[:\- ]*\|)+[\:\- ]*\n/

Behavioral check confirms literal-hyphen semantics — /[a\- ]/ matches -, a, and space, but not z.

Added a runtime regression test (escaped_hyphen_in_class_stays_literal) covering both the translation output and that the previously-crashing patterns construct. All 9 regex:: tests pass; cargo fmt --check clean.

This unblocks a native build of marked (#4362 fixed codegen+link; this was the last blocker — the binary now boots instead of throwing on module-init regex).