feat(point-of-sale): add resolution target types for cart and payment validations

[vctrchu]

Resolves https://github.com/shop/issues-retail/issues/33801

Background

POS intercept extensions (shopify.intercept('cartvalidations' | 'paymentvalidations', ...)) block a workflow by returning an ERROR-level validationAdd. When that happens, POS opens an app-owned remediation UI inside its resolution flow. Each interceptable event gets its own dedicated resolution render target so the public types can express per-event API availability.

This adds the TypeScript contracts for those targets. Everything lands @private, matching the rest of the intercept type family, until early access.

Solution

Two new render targets in RenderExtensionTargets:

• pos.cart.validations.resolution.render — Standard APIs + Scanner + mutating Cart + ResolutionApi<CartValidationsEvent>
• pos.payment.validations.resolution.render — Standard APIs + Scanner + read-only Cart + ResolutionApi<PaymentValidationsEvent>

The cart is frozen during payment, so the payment target reuses ReadonlyCartApi; the cart target mutates via the existing CartApi. Neither target exposes the Action API (resolution is host-invoked, not merchant-invoked) or domain-scoped APIs.

New supporting types:

• ResolutionApi<TEventData> — target-scoped shopify.resolution.event signal carrying the intercepted event's data (CartValidationsEventData, PaymentValidationsEventData — the same fields the interceptor sees, without the DOM Event base), typed per event rather than as one broad union.
• ResolutionComponents — all standard components except Page, POSBlock/PosBlock, and Tile, since resolution UI renders inside a POS-owned flow step.

The tester's PosMockFactory map is exhaustively keyed over all POS targets, so mock factories for both new targets are included, with tests covering the mutating/read-only cart split and the resolution event shape.

🎩

• yarn build, yarn test (64 tests incl. 6 new in pos-resolution-targets.test.ts), eslint + prettier on touched files — all green

Checklist

• I have 🎩'd these changes
• I have updated relevant documentation

[vctrchu]

/snapit

[shopify-github-actions-access]

🫰✨ Thanks @vctrchu! Your snapshots have been published to npm.

Test the snapshots by updating your package.json with the newly published versions:

"@shopify/ui-extensions": "0.0.0-snapshot-20260820182142",
"@shopify/ui-extensions-tester": "0.0.0-snapshot-20260820182142"

[vctrchu]

/snapit

[shopify-github-actions-access]

🫰✨ Thanks @vctrchu! Your snapshots have been published to npm.

Test the snapshots by updating your package.json with the newly published versions:

"@shopify/ui-extensions": "0.0.0-snapshot-20260820185458",
"@shopify/ui-extensions-tester": "0.0.0-snapshot-20260820185458"

[vctrchu]

/snapit

[shopify-github-actions-access]

🫰✨ Thanks @vctrchu! Your snapshots have been published to npm.

Test the snapshots by updating your package.json with the newly published versions:

"@shopify/ui-extensions": "0.0.0-snapshot-20260820191219",
"@shopify/ui-extensions-tester": "0.0.0-snapshot-20260820191219"