[rcaplanshopify]

What

Port of #4763 to 2026-10.

• Bump @shopify/generate-docs from 1.2.2 to 1.3.0 (Shopify/generate-docs#463) and pass its new opt-in --strictInput flag when building the checkout and customer account docs. Admin and POS are unchanged.
• Regenerate the checkout docs for 2026-10. Customer account output is byte-identical to 2026-10 docs: generate customer account data without checkout's types; fix checkout wording #4751, so nothing to commit there.

Why

Without --strictInput, every @publicDocs type reachable from --input becomes a documentation root, including types imported from other surfaces. Customer account docs ended up documenting 140 checkout-only types and resolving 86 same-named types (Attribute, CartLine, Country, …) to checkout's definition instead of its own; #4751 worked around that by hand. With the flag, only types defined inside --input are roots.

Verification

Generated locally with 1.3.0, with and without the flag:

• Customer account: output with the flag matches 2026-10 docs: generate customer account data without checkout's types; fix checkout wording #4751's committed file byte for byte. Without the flag: 140 extra types, 86 mis-resolved.
• Checkout: only ValidationError changes. It previously resolved to the unrelated ValidationError in src/shared.ts (type/code/issues); it now resolves to src/surfaces/checkout/api/shared.ts (message/target), which is the one the docs describe.
• Every typeName referenced by shopify-dev's 2026-10 MDX (161 checkout, 151 customer account) still resolves.
• targets.json is byte-identical with and without the flag for both surfaces.

yarn.lock also picks up entries for @arethetypeswrong/cli and publint, which #4645 added to packages/ui-extensions/package.json without updating the root lockfile.

Checklist

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

[github-actions]

This PR targets a stable release branch (2026-10). Once merged, the change typically also needs to be forward-ported to 2027-01-rc so it ships in the next release.

When you open the forward-port PR, include a line like this in its body so the needs-rc-port label gets removed automatically when that PR merges:

Forward-port of #4764

Accepted formats (comma-separated for multiple):

• #4764
• GH-4764
• 4764
• https://github.com/Shopify/ui-extensions/pull/4764

If a forward-port isn't needed (e.g., the change is stable-only), you can remove the needs-rc-port label manually.

[github-actions]

We detected some changes in packages/*/package.json or packages/*/src, and there are no updates in the .changeset directory. If the changes are user-facing and should cause a version bump, run yarn changeset to track your changes and include them in the next release CHANGELOG. If you are making simple updates to repo configuration, examples, or documentation, you do not need to add a changeset.