fix: Android 3-digit hex + iOS UPC-A, repair toolchain, replace CI

[vittoridavide]

What

Repairs a broken dev toolchain, fixes one Android rendering bug, and replaces a CI pipeline that could not run.

fix: 3-digit hex colors on Android

BarcodeView.handleColor expanded #RGB by concatenating the digits rather than doubling them, so #0AF became #0AF0AF instead of #00AAFF. iOS already expanded correctly, so the two platforms disagreed on every shorthand color.

Verified on a physical device (Huawei JNY-LX1, RN 0.83): two QR codes rendered side by side with #0AF and #00AAFF now sample to identical pixels.

chore: toolchain repair

• babel.config.js referenced metro-react-native-babel-preset, replaced by @react-native/babel-preset in RN 0.73 and no longer installed. Jest could not transform anything and ESLint failed to parse any file it read through Babel.
• typecheck now runs against tsconfig.build.json. The root config also pulls in example/, whose @/* aliases are invisible from the root and whose react-native@0.83.2 collides with the root's 0.73.2 — both declare the same ambient codegenNativeComponent module with incompatible HostComponent<P> definitions.
• Dropped @types/react-native (obsolete since RN 0.71 ships its own types) and the resolutions pin holding @types/react at 17, which was also forcing 17 onto the example app that needs 19.
• Stopped linting Expo's generated, gitignored expo-env.d.ts.

ci: CircleCI → GitHub Actions

The CircleCI config ran circleci/node:10 against a package requiring Node >= 18 and pinning Yarn 3.6.1, with Yarn v1 install flags that Yarn 3 rejects. It also invoked yarn typescript, a script that no longer exists.

style: / docs:

Prettier formatting across src/ and example/, and a new CLAUDE.md.

Checks

yarn lint, yarn typecheck, yarn test, and yarn prepare all pass locally.

Notes

• yarn lint still emits 35 warnings, all in example/ — 34 are react/react-in-jsx-scope false positives from @react-native/eslint-config@0.72.2 predating the automatic JSX runtime. Warnings only; lint exits 0.
• yarn test runs a single it.todo placeholder. There is no real coverage yet.
• Running on RN 0.83 surfaced a deprecation warning for the deep import in src/BarcodeCreatorNativeComponent.ts; not addressed here.

[vittoridavide]

Added: iOS UPC-A fix

Running the example on an iOS simulator (first iOS build in this branch) surfaced a second, pre-existing bug: UPC-A rendered nothing on iOS, while Android rendered it fine.

CIEANBarcodeGenerator.checkSum() weighted digits from the left — x1, x3, x1, … — which is the EAN-13 rule. On a 12-digit UPC-A the weights land on the wrong parity, so validation failed, drawOutputImage() returned nil, and the view stayed blank. drawUPCA() was correct and simply never reached.

For the example's own 036000291452:

as written (EAN-13 weighting):  8  -> rejected
correct UPC-A weighting:        0  -> valid

The check digit is always rightmost and always counts x1, so anchoring the alternation there is correct for both lengths.

Verified on iPhone 17 Pro simulator, sampling the UPC-A cell:

	before	after
UPC-A	100% background (blank)	47.1% black / 46.5% white
EAN-13	rendering	still rendering

Also verified on both platforms that #0AF and #00AAFF now produce identical pixels, which was the point of the Android fix.

Known remaining divergence (not addressed here)

iOS requires exactly 12 digits with a valid check digit for UPC-A (13 for EAN-13). Android accepts ^\d{11,12}$ / ^\d{12,13}$ and lets ZXing compute the check digit. So an 11-digit UPC-A still renders on Android and stays blank on iOS. That is a design decision rather than a bug, and is left for a follow-up.