Add private positioning types to s-box checkout component

[oliverigor]

Adds the private positioning types for the s-box checkout component, mirroring the host-side change merged in shop/world#957019 and shop/world#992474

What

• packages/ui-extensions/src/surfaces/checkout/components/Box.d.ts: adds the four new @private props to BoxElementProps, copied verbatim from the build-components output in checkout-web:
  • position?: 'absolute' | 'relative' (default 'relative')
  • insetBlock? / insetInline?: `auto ${SizeUnits}` | `${SizeUnits} auto` | 'auto' (default 'auto')
  • transform?: translate(...) forms using SizeUnits, or 'none' (default 'none')
• Adds a patch changeset.

Notes

• Only the new-prop hunks were applied instead of wholesale copying the generated files.

[oliverigor]

/snapit

[shopify-github-actions-access]

🫰✨ Thanks @oliverigor! 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-20260829123027",
"@shopify/ui-extensions-tester": "0.0.0-snapshot-20260829123027"

[patjakubik]

Any chance to make this available for everyone? Many apps devs are affected and we are getting close to deadline. https://community.shopify.dev/t/migrating-to-polaris-web-components-some-rough-edges/23401