`^` with a negative exponent puts `0.5` and `Infinity` into an `Int`

Repository: gren-lang/core
Found against: gren 0.6.6, gren-lang/core 7.4.2, node 22

Summary

^ is Math.pow with no integer case, so an Int-typed expression evaluates
to a fraction, or to Infinity:

2 ^ -1      --> 0.5         -- typed Int
0 ^ -1      --> Infinity    -- typed Int

Both are reachable with a computed exponent, no cast, no Float anywhere in
the expression, and no warning. String.fromInt on the first prints 0.5.

Reproduction

Operands are computed rather than literal, so this is not constant folding, and
both the inlined and the kernel path are shown, in case the two ever differ as
they do for // (#383):

apply : (Int -> Int -> Int) -> Int -> Int -> Int
apply f a b =
    f a b


two : Int
two =
    String.count "ab"


minusOne : Int
minusOne =
    negate (String.count "a")

Cause

core/src/Gren/Kernel/Basics.js:

var _Basics_pow = F2(Math.pow);

Math.pow is the float operation. Elm has the same definition and the same
behaviour, so this is inherited rather than introduced.

Start with core/src/Gren/Kernel/Basics.js and the _Basics_pow definition, then reproduce the three expressions from the issue with the inlined and kernel paths. Determine the intended behavior for negative exponents on Int values; done means those expressions no longer produce fractional or Infinity results while preserving the documented integer typing.