Add package-size PR comments

[kiftio]

Stack Context

This stack adds a non-required package-size signal for Checkout Kit PRs, then trims RN package-only test files that the size report makes visible.

Why?

PR builds currently do not surface published artifact-size changes. This adds a PR-only workflow that measures package artifacts from the PR base SHA and PR head SHA, then updates a sticky PR comment with base/head/delta rows.

The workflow intentionally stays out of CI Required. It adds extra latency by measuring both sides of the diff, but it does not block merging when the required CI suite is green.

What gets measured?

Platform	Technique	What it tells us	Limitation
Web	Runs pnpm build, then pnpm pack, and reports the generated npm tarball size.	Size of the @shopify/checkout-kit package as published to npm.	Not a consumer bundle-size metric. It does not account for app bundler settings, tree shaking, minification, gzip/brotli at delivery, or downstream usage patterns.
React Native	Runs pnpm module clean, pnpm module build, then pnpm pack inside the RN module package.	Size of the @shopify/checkout-kit-react-native npm package: JS outputs, TS/source files, native bridge source, podspec/Gradle config, and bundled protocol package files.	Not full client impact. The RN package declares native Checkout Kit dependencies that CocoaPods/Gradle resolve later, so this number does not include the Swift Checkout Kit SDK or Android com.shopify:checkout-kit AAR in a consuming app.
Android	Runs ./gradlew :lib:assembleRelease and reports platforms/android/lib/build/outputs/aar/lib-release.aar.	Size of the Android library artifact consumers receive from Maven.	Not final app binary size. Consuming apps may shrink, optimize, or package the dependency differently with R8/resource shrinking and their own build settings.

How are deltas calculated?

The workflow checks out both sides of the PR:

• base: github.event.pull_request.base.sha
• head: github.event.pull_request.head.sha

That makes the delta stack-aware. For example, a stacked PR compares against its parent PR branch rather than origin/main, so the comment reflects only the package-size impact of that PR in the stack.

If base measurement fails, the workflow still measures the head and renders the base/delta cells as unavailable.

Why no Swift yet?

Swift/SPM does not publish a single binary artifact in this repo. It ships source/resources through Swift Package Manager, and the CocoaPods spec is also source-based. We could cheaply measure an SPM or CocoaPods source/resource payload, but that is a different kind of signal from npm tarballs and the Android AAR.

For now this PR skips Swift so the comment stays focused on directly published package artifacts. A follow-up could add a clearly labeled Swift — SPM source/resource payload row if that signal becomes useful.

[kiftio]

• Remove native test files from RN package #310
• Add package-size PR comments #309 👈 (View in Graphite)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[github-actions]

Package Size

Platform	Artifact	Base	Head	Delta
Web	npm tarball	56.7 KiB	56.7 KiB	0 B
React Native	npm tarball	93.9 KiB	93.9 KiB	0 B
Android	release AAR	613.4 KiB	613.4 KiB	0 B

Measured from the PR base SHA and PR head SHA. This comment reports package artifact sizes only; it is not a final app binary-size report.