fix(math fns) Math.min/Math.max truncating Float (and String) arguments

[arthurmaciel]

Problem

Math.min / Math.max are polymorphic — a -> a -> a ("any comparable type",
per Sky.Core.Math). But the Go backend coerced their arguments through AsInt:

• the typed-companion pass emitted rt.Math_minT(rt.AsInt(x), rt.AsInt(y))
  (typedKernelArgCoerce + typedKernelLiterals), and
• the polymorphic fallback rt.Math_min / rt.Math_max also compared via AsInt.

So a Float Math.min / max truncated to Int. The range of [0.4 … 1.3]
collapses to 0..1, which mis-scales every Std.Ui.Chart sparkline and heatmap —
the heatmap renders a single cell instead of the full grid. String args were
meaningless too.

-- range computed with Math.min / Math.max over a List Float
Chart.heatmap cfg grid
Chart.sparkline cfg [ 0.4, 0.6, 0.5, 0.8, 0.7, 0.9, 1.0, 0.95, 1.2, 1.15, 1.3 ]

Before / After

Fix

1. rt.Math_min / rt.Math_max compare via skyLessThan (the polymorphic
   comparator already used by List_sortBy) instead of AsInt.
2. Drop Math.min / Math.max from typedKernelArgCoerce + typedKernelLiterals
   so they lower to the now-correct polymorphic kernel; the use-site coercion
   narrows the result.
3. Same float/string-aware comparison in the runtimeGoSource fallback.

Math.abs is intentionally left untouched — its Sky type is Int -> Int, so
AsInt is correct.

Tests

runtime-go/rt/math_minmax_poly_test.go covers Float / Int / String min/max.
go test ./rt/ passes.

Related — Elm conformance

Sky.Core.Math mirrors Elm's
Basics; this
restores min / max to Elm's polymorphic comparable -> comparable -> comparable.
It may be worth a broader review of Sky's conformance to Elm Basics — for
example, Elm's abs : number -> number accepts Float, whereas Sky's abs is
currently Int -> Int.

[anzellai]

it makes sense, yes Go's side of AsInt is kind of annoying as that's underlying Go's int type, doesn't cover Elm's equivalent or Go's comparable. Perhaps I need to use Go's generic here with AsNum, I will have a proper think after v0.17 is shipped.
thanks!