- detect and forbid non-positive size casts
- detect and forbid negative struct pattern literal indices
- avoid invalid constant folding of negative based literals

- split out typeof handling of part selects
- account for directionality of base dimension
- refactor dimensions test case with detailed output

- ensure concats and repeats stay unsigned
- defer unbased-unsized conversion to enable cast semantics
- disable inaccurate folding of binary operations of based numbers
- fix typeof and size cast binop signedness logic
- fix typeof $unsigned and $signed
- test harness allows production of `integer unsigned`

- number literals are parsed rather than stored as strings
- fix array query functions used on non-trivial number literals
- more efficient expression simplification recursion
- expanded constant folding scenarios