[Customer account UI extensions 2025-10]: Set up component sidebar

[mcvinci]

This PR:

• Adds .doc.ts files, thumbnail visuals, and examples for ~55 shared checkout components to the customer account surface, so component reference pages are generated directly instead of linking out to checkout
• Updates the build script to resolve checkout component types during doc generation by copying .d.ts files to temporary .ts files and passing checkout as a --typesInput source
• Aligns subcategories across shared component content to match the new sidebar IA (for example, "Feedback" → "Feedback and status indicators", "Interactive" → "Media and visuals", "Other" → "Media and visuals")
• Relates to https://github.com/shop/world/pull/486452
• Partially closes https://github.com/Shopify/shopify-dev/issues/69153

[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.