Implement gawk array sorting and type-introspection builtins

[bertysentry]

This is a focused follow-up to umbrella issue #80. The latest mvn verify run for GawkCompatibilityIT shows a concrete compatibility cluster around gawk's array sorting and type-introspection features.

Observed impact:

• 13 failing Gawk compatibility cases in the latest run
• Representative cases: �sort, �sorti, �asort, �asorti, �sortbool, �sortsymtab, sort1, �rraytype, mdim1, ypeof2, ypeof4, ypeof5, ypeof6
• Current failure mode is typically SemanticException: function ... (asort|asorti|typeof)

The failing cases suggest that we need more than stub builtin registration. Jawk also needs the corresponding runtime behavior that gawk expects for:

• �sort()
• �sorti()
• ypeof()
• typed / untyped / array value distinctions that those functions expose

Acceptance criteria:

• the representative cases above pass in GawkCompatibilityIT
• �sort() and �sorti() work on plain arrays and nested arrays where gawk allows them
• ypeof() returns gawk-compatible categories for the cases covered by the suite
• sorting and introspection behavior is wired into the real runtime model, not only the parser