v1.17.8 — TypeScript port of expr-lang/expr v1.17.8

Full TypeScript port of the Go expr-lang/expr expression language engine.

Highlights:
- Dual output: ESM + CJS + type declarations
- 60+ builtin functions (len, max, min, sum, type, keys, values, sort, string/math/date helpers)
- Full language surface: arithmetic, comparison, logical, bitwise operators
- Ternary, let declarations, sequences, member access, optional chaining, slicing, ranges
- Pipes, nil-coalescing, predicates (all/any/none/one/filter/map/count/find/groupBy/sortBy/reduce)
- Optional compile-time type checker (Env)
- Optimizer (constant folding, predicate fusion, etc.)
- AST patchers, custom functions, operator overloading
- Zero runtime dependencies
- Parity testing infrastructure with Go fixture generator

Go numeric model preserved: int/int64 -> bigint, float64 -> number.