tree-sitter-pascal is not on PyPI so extract_pascal() fell back to an
empty error result for all users. _extract_pascal_regex() now handles
unit/program/library headers, uses clauses, class/interface declarations
with inheritance, forward method decls, qualified impl headers, balanced
begin/end body extraction, and intra-file calls edges. All 15 previously
skipped pascal_required tests now run unconditionally and pass.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>