[Android] Add advanced present builder callbacks and migrate sample flow

[tiagocandido]

What changes are you making?

This PR adds a Kotlin-first per-presentation builder for ShopifyCheckoutKit.present(checkoutUrl, activity) { ... } and migrates the Android sample to that path.

• Introduces CheckoutPresentation, which exposes builder hooks for onComplete, onFail, onCancel, connect, onShowFileChooser, onGeolocationPermissionsShowPrompt, onGeolocationPermissionsHidePrompt, and onPermissionRequest.
• Adds a new Kotlin-facing ShopifyCheckoutKit.present(checkoutUrl, context, configure) overload that builds a DefaultCheckoutEventProcessor internally, while keeping the existing DefaultCheckoutEventProcessor overload for Java and reusable-object integrations.
• Adds dedicated CheckoutPresentationTest coverage for lifecycle callbacks, optional browser/system callbacks, and forwarding a connected CheckoutCommunicationClient, and regenerates lib/api/lib.api for the new API surface.
• Migrates samples/MobileBuyIntegration off MobileBuyEventProcessor: checkout completion/failure/cancel handling now lives in CartViewModel, browser/system callbacks route through MainActivity, and typed CheckoutProtocol.Client notifications are connected inline from the builder.
• Updates the Android README and sample README to center the builder-based presentation API and remove outdated or duplicated callback guidance.

How to test

From platforms/android/:

./gradlew :lib:testDebugUnitTest :lib:detekt :lib:lintDebug

From platforms/android/samples/MobileBuyIntegration/:

./gradlew :app:assembleDebug :app:lintDebug

Manual sanity in the sample app:

• Add an item to cart and open checkout from the cart screen.
• Complete checkout and confirm the cart clears and navigation returns to product browsing.
• Close checkout and verify cancel logging still flows through CartViewModel.
• Exercise a file upload / camera flow and a geolocation prompt from checkout to confirm the host callbacks are routed through MainActivity.
• Confirm typed CheckoutProtocol.Client notifications still log from the sample flow.

---

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

Releasing a new Android version?

• I have bumped the versionName in platforms/android/lib/build.gradle
• I have updated platforms/android/CHANGELOG.md
• 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.

[tiagocandido]

• [Android] Add advanced present builder callbacks and migrate sample flow #112 👈 (View in Graphite)
• [Android] Add window.open UCP delegation #107
• main

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

[kieran-osgood-shopify]

complete should exist in the protocol instead now right?

[tiagocandido]

Yep, agreed. complete now lives on the protocol path, same as Swift. I removed builder-level onComplete; the builder just handles fail/cancel and host callbacks now.

[graphite-app]

Merge activity

• May 15, 10:51 AM UTC: This pull request can not be added to the Graphite merge queue. Please try rebasing and resubmitting to merge when ready.
• May 15, 10:51 AM UTC: Graphite disabled "merge when ready" on this PR due to: a merge conflict with the target branch; resolve the conflict and try again..

[kieran-osgood-shopify]

This callback can be dropped here now right?