Support UI extensions

[pbennett1-godaddy]

Summary

Adds Phase 1 checkout UI extension runtime support to @godaddy/react.

This introduces a production-shaped bridge runtime that can discover enabled store UI extensions, load deterministic CDN-hosted DOM bundles, and mount them into checkout target slots without blocking
checkout. Phase 1 intentionally supports trusted in-page DOM bundles while preserving runtime seams for a future worker/SDK-based UI extension architecture.

Key goals addressed:

• Load enabled UI extensions for a target from checkout-api or provided checkout session app data.
• Build deterministic extension bundle URLs from cdnUrl, target, applicationId, and releaseId.
• Mount each extension into a host-owned checkout target container.
• Pass only minimized checkout context plus consumer-owned initialProps.
• Keep checkout resilient when extension loading, registration, mount, update, or unmount fails.
• Add structured runtime errors for observability.
• Keep debug behavior diagnostic-only through GoDaddyProvider debug logging, without changing runtime behavior.

Changeset

• Changeset added (docs)

Test Plan

Validated locally with:

pnpm --filter @godaddy/react typecheck                                                                                                                                                                  
pnpm --filter @godaddy/react test -- --runInBand                                                                                                                                                        
pnpm --filter @godaddy/react lint                                                                                                                                                                       
pnpm --filter @godaddy/react build                                                                                                                                                                      

Results:

• Typecheck passes.
• React package test suite passes.
• Biome lint/check passes.
• React package build succeeds, including the new @godaddy/react/ui-extensions subpath export.

Additional coverage added for:

• Deterministic UI extension script URL construction.
• Missing required script URL fields.
• DOM bundle registration and mount lifecycle.
• Invalid DOM bundle contracts.
• Runtime update and unmount lifecycle.
• Unmount-before-script-load behavior.
• Queued updates while an extension bundle is still loading.
• Target behavior with provided app data.
• Target behavior with checkout-api response data.
• Provider debug mode continuing to render runtime containers instead of JSON.
• Grouping multiple UI extensions by target without duplicating app entries.

[changeset-bot]

🦋 Changeset detected

Latest commit: 2719c26

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@godaddy/react	Patch
nextjs	Patch

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[wcole1-godaddy]

Thanks for the work here. The runtime shape looks good overall, and the React package checks are green from my local pass after building the workspace dependency.

Before approval, I think we should tighten up these three items:

1. Clean up failed or timed-out mounts

   In packages/react/src/ui-extensions/runtime/dom-bundle-runtime.ts, once contract.mount() has been invoked, a rejection or timeout can leave partial DOM/listener work behind. Because hasMounted only flips after mount completes, a later unmount() clears runtime state without calling the extension's unmount(). Please attempt cleanup when mount fails or times out after a contract exists.

2. Wrap shipping notes with the new notes targets

   Pickup and standalone notes now render checkout.form.notes.before / checkout.form.notes.after, but the shipping notes path still renders a plain <NotesForm /> in packages/react/src/components/checkout/form/checkout-form.tsx. Please add the same target wrappers there so notes extensions work consistently for shipping-enabled checkouts.

3. Do not render discovery errors directly to shoppers

   packages/react/src/ui-extensions/target.tsx currently renders hook/discovery errors as a visible <pre>. Since extension discovery failure should not affect checkout UX, please route that through onExtensionError, debug-only output, or silent logging instead of rendering the error by default.

[wcole1-godaddy]

Approved after review. I found no blocking issues in the current diff.\n\nValidated locally in a clean temp worktree after building @godaddy/localizations:\n- corepack pnpm --filter @godaddy/react typecheck\n- corepack pnpm --filter @godaddy/react test\n- corepack pnpm --filter @godaddy/react build\n- corepack pnpm --filter @godaddy/react lint