[E2E] Prepare native preload ready-flow validation

[kyle-schellen]

What changed

• e2e/tests/shared/native-preload-ready.yaml — top-level test, tagged preload/smoke.
• e2e/flows/checkout/assert-native-preload-ready.yaml — reusable subflow.
• e2e/config/matrix.yml — Swift and Kotlin adopt preload. React Native is unchanged.
• e2e/scripts/execute_browserstack_run + e2e/lib/ — request device logs, then verify the Android cache-hit line in the passing testcase's log artifact.

Why

Presenting checkout is not proof that preload was reused. This asserts the whole chain:

preload-state-ready  →  cached WebView selected  →  real checkout content

Cache use is read per platform: iOS asserts the diagnostic in the sample's Settings → Logs screen inside the flow; Android verifies Returning cached preloaded WebView. in the BrowserStack device log afterwards, and rejects the concurrent-fresh message.

No queue case, no timing threshold, no new public SDK API.

Testing

Physical devices, all four targets green:

Target	Device
swift-ios	iPhone 15, iOS 27 Beta
kotlin-android	Google Pixel 9, Android 17.0
react-native-ios / react-native-android	unchanged, still green

The Android leg proves the artifact downloader against live BrowserStack URLs: its verification raises unless the log is fetched and contains the cache-hit signal.

Also run locally on simulator and emulator via dev swift e2e --tags preload and dev android e2e --tags preload, plus the Ruby, Swift, and Android suites and lint.

Stack

1. [E2E] Expose native preload state markers #626 — preload state markers in the samples
2. [E2E] Log ready Swift preload cache hits #627 — Swift ready cache-hit diagnostic
3. [E2E] Prepare native preload ready-flow validation #631 — this PR: the E2E test, matrix wiring, and BrowserStack validation

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Before you merge

Important

• I've added tests to support my implementation
• I have read and agree with the Contribution Guidelines
• I have read and agree with the Code of Conduct
• I've updated the relevant platform README (platforms/swift/README.md and/or platforms/android/README.md)

---

Releasing a new Swift version?

• I have bumped the version in ShopifyCheckoutKit.podspec
• I have bumped the version in platforms/swift/Sources/ShopifyCheckoutKit/ShopifyCheckoutKit.swift
• I have updated the SwiftPM/CocoaPods version snippets in platforms/swift/README.md (major version only)

Releasing a new Embedded Checkout Protocol version?

• I have bumped embeddedCheckoutProtocolAndroid in platforms/android/gradle/libs.versions.toml
• I have updated protocol/languages/kotlin/embedded-checkout-protocol/api/embedded-checkout-protocol.api if the public API changed

Releasing a new Android version?

• I have bumped checkoutKitAndroid in platforms/android/gradle/libs.versions.toml
• I have updated the Gradle/Maven version snippets in platforms/android/README.md

Tip

See the Contributing documentation for the full release process per platform.

[kyle-schellen]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• [E2E] Prepare native preload ready-flow validation #631 👈 (View in Graphite)
• [E2E] Log ready Swift preload cache hits #627
• [E2E] Expose native preload state markers #626
• main

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

[bitrise]

Install this build

Open Tophat, select your target device, then click Install. Links open on the Mac running Tophat.

SDK	Install
React Native	Install with Tophat
Swift	Install with Tophat
Kotlin	Install with Tophat

Checkout Kit E2E results

Status	Suite	Target	Platform	OS version tag	Device
✅	react-native-ios	react-native	ios	latest	iPhone 15 iOS 27 Beta
✅	react-native-android	react-native	android	latest	Google Pixel 9 Android 17.0
✅	kotlin-android	kotlin	android	latest	Google Pixel 9 Android 17.0
✅	swift-ios	swift	ios	latest	iPhone 15 iOS 27 Beta