[E2E][Bug] fix flaky E2E order confirmation detection

[kieran-osgood-shopify]

Why

The required E2E gate intermittently closed checkout before order completion and then failed because the host cart had not been cleared.

BrowserStack command logs showed the existing broad completion regex returning only 250 ms after Pay now, while the payment spinner was still visible. The test then tapped the checkout close button. Later passing runs using the exact same APK and journey waited 976 ms and 4.8 seconds for the real confirmation state before closing.

Fix

Match complete order-confirmation headings instead of arbitrary text containing Thank you, Your order, Order confirmed, or confirmation.

Both shared order journeys now accept only:

Thank you[, name][!]
Your order is confirmed
Order confirmed
Order confirmation

How to test

GIVEN the PR's Kotlin Android checkout-guest BrowserStack journey has submitted payment

WHEN the reviewer watches the journey recording from the Pay now action through checkout closing

THEN checkout should remain open while payment is processing and close only after the order-confirmation heading appears

AND the host app should show an empty cart after checkout closes

---

GIVEN the PR's hardcoded-buyer-identity BrowserStack journey has submitted payment

WHEN the reviewer watches the journey recording from the final submit action through checkout closing

THEN checkout should remain open until a complete order-confirmation heading appears

AND the host app should show an empty cart after checkout closes

Evidence

• Failing required-gate pipeline: https://app.bitrise.io/app/f51f9054-053e-40f1-81e9-ae727567ae76/pipelines/461f6408-9f86-4824-92f8-59ee36b89606
• Passing full E2E pipeline with the focused selector: https://app.bitrise.io/app/f51f9054-053e-40f1-81e9-ae727567ae76/pipelines/29e34964-3d75-4679-8c89-27f6a59cbdad

[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	Tags	Target	Platform	OS version tag	Device
✅	launch, checkout-presentation, checkout-completion, buyer-identity	react-native	ios	latest	iPhone 15 iOS 27 Beta
✅	launch, checkout-presentation, checkout-completion, buyer-identity	react-native	android	latest	Google Pixel 9 Android 17.0
✅	launch, checkout-presentation, checkout-completion, buyer-identity, preload	kotlin	android	latest	Google Pixel 9 Android 17.0
✅	launch, checkout-presentation, checkout-completion, buyer-identity, preload	swift	ios	latest	iPhone 15 iOS 27 Beta