perf: optimize literal classification and extend numeric literal support

This PR optimizes literal recognition and improves `grind` support for rational and signed fixed-width integer literals.

Replace value-extractor calls with direct Boolean checks. Add scientific `Rat` recognition and `Int8`/`Int16`/`Int32`/`Int64` extraction and normalization. Fix interpretation of aliased types and handling of literals in match conditions. Add consistency tests covering wrapping, boundaries, metadata, and metavariables.