fix(transforms): treat scale percentage values as unitless (#216)

[YevheniiKotyrlo]

Summary

Tailwind v4 scale-* utilities crash React Native's transform validator on native:

Invariant Violation: Transform with key of "scale" must be a number: {"scale":"75%"}

CSS scale accepts percentages (75% is a 0.75 factor), but RN's transform validator only accepts unitless numbers. The "75%" string reached the validator through two independent code paths, both fixed here:

1. Compile-time (parseScaleValue) delegated unconditionally to parseLength, which formats a lightningcss { type: "percentage", value: 0.75 } back into the string "75%" — correct for layout props like width, wrong for transforms. Short-circuit percentages to return the already-normalised decimal.

2. Runtime (scale() resolver) accepted string args as valid because its guard is typeof x === "string" || typeof x === "number". This is the path Tailwind v4 actually hits — scale-75 emits scale: var(--tw-scale-x) var(--tw-scale-y) whose vars resolve to "75%" at runtime, bypassing (1). Normalize "N%" → N/100 before the guards. rotate keeps "Ndeg" and translate keeps "N%" — only scale is unitless.

Fixes #216.

Reproduction (before this PR)

<View className="scale-75 h-20 w-20 bg-red-500" />

Crashes on first render with Transform with key of "scale" must be a number: {"scale":"75%"}.

Test plan

• New edge-case tests in native/transform.test.tsx: single %, identity (100% → 1), zero (0% → 0), negative flip (-50% → -0.5), > 100% (150% → 1.5), fractional (12.5% → 0.125), per-axis (scale: 75% 50%), both var() shapes (the Tailwind emission, same and different per-axis), and a unitless-number regression guard (scale: 2 stays 2).
• Corrected the pre-existing scale — unparsed test and the vendor Transforms - Scale tests (scale-0 / scale-x-50 / scale-y-50 / scale-50) that had encoded the buggy "N%" output (they passed while the behaviour was broken).
• rotate / translate tests unchanged — only scale normalizes % → unitless.
• yarn test, yarn typecheck, eslint, prettier pass. (The three babel suites fail identically on clean main in this environment — missing --experimental-vm-modules — and are unrelated.)