feat: emit native token outputs for iOS (Swift) and Android (Kotlin)

[thomasdigby]

Closes #52

What

The build now emits tokens in native-consumable form alongside the existing outputs in lib/, per theme:

• lib/theme-*.swift — a public enum ThemeTokens of SwiftUI Color(red:green:blue:opacity:) and CGFloat constants
• lib/theme-*.kt — a Compose object ThemeTokens (package uk.co.atomlearning.theme) of Color(0xAARRGGBB), .sp / .dp constants

How

Rather than hand-rolling the conversions, this uses style-dictionary's built-in formats and transforms (ios-swift/enum.swift, compose/object; color/ColorSwiftUI, color/composeColor, size/swift/remToCGFloat, size/compose/remToSp|Dp). To enable that, the token sources are migrated to the DTCG format ($value, plus group-level $type), which is what the built-in transforms key off.

Custom code is reduced to src/native.ts:

• the name/native/camel transform — the flat camelCase naming contract (color.blue.800 → blue800, color.subject.gcse-maths → subjectGcseMaths, size.font.sm → fontSm); these names are the native apps' API, renames are breaking
• the file filter — token coverage (colours, size.font|leading|radii|space; font stacks/breakpoints/effects excluded per the issue) and per-theme scoping

size.leading deliberately has no transform — the unitless multipliers pass through as-is.

Web outputs unchanged — verified byte-identical

The previously-listed color/hsl and size/rem transforms were silent no-ops (they filter on $type, which no token declared); they're removed from the web platforms so the DTCG migration cannot alter web output. All 15 web artifacts (*.css, *.js, *.d.ts, themes.css, media.*) were diffed byte-for-byte against a pre-migration build: identical.

Test coverage (135 tests, was 37)

This PR also closes long-standing gaps in output coverage:

• CI (.github/workflows/ci.yml) — the repo had none. Runs build + tests + tsc on every PR, with a macOS job that installs swiftc/kotlinc
• pretest hooks — yarn test/test:run now build first, so the suite can't pass against stale lib/ (we hit exactly that during development)
• test/completeness.test.ts — reconciles source tokens against every output. Previously nothing asserted that all tokens reach the outputs; now a filter regression that silently drops e.g. color.gl.* fails the build
• test/values.test.ts — exact shadow / breakpoint / font-stack values (shadows were only checked as a wildcard reset before) and cross-output consistency: Swift colours are re-derived from the source hsl() and checked against both the JS theme and the Kotlin ARGB output
• test/native-compile.test.ts — compiles every generated file with swiftc and kotlinc (against minimal Compose stubs). Verified locally with a real kotlinc; skips cleanly when the toolchain is absent
• test/assets.test.ts — lib/assets/ had zero coverage despite backing ~20 export paths. Now every export target, typesVersions path and copied asset is checked for existence, non-emptiness and file signature

All new suites were mutation-tested (dropping one Swift constant and emptying one asset produced 7 failures), so they're not passing vacuously.

Pre-existing bug found, not fixed

The new completeness test surfaced a real defect that predates this PR: the CSS formatters build names from property.name, emitting --color-coolGrey-100, while the JS/.d.ts properties map kebab-cases it to --color-cool-grey-100. So var(--color-cool-grey-100) resolves to nothing in CSS. It's encoded as an it.fails expected failure with a comment rather than hidden — fixing it changes published CSS variable names, so it's a call for you to make (either rename the CSS vars to kebab or stop kebab-casing in the JS map).

Also note the build's "Token collisions detected" warnings pre-date this PR (intentional theme overrides of base tokens).

Token coverage

Group	Emit as	Conversion
color.*	Color	hsl()/hex → sRGB at build time; alpha tokens carry their opacity
size.font.*	CGFloat / TextUnit	rem × 16 (sm 0.875 → CGFloat(14.00) / 14.00.sp)
size.radii.* / size.space.*	CGFloat / Dp	rem × 16
size.leading.*	number	unitless multipliers, as-is

No packaging changes: files: ["lib"] already ships the new files; the native repos vendor them for a pinned version (e.g. via unpkg).

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