A Custom Shopify Theme, Generated as Liquid Code

Build a Shopify storefront theme for a small stationery brand. Use configurable sections for collections, product details and editorial stories while preserving Shopify's cart and checkout behaviour.

Include these capabilities:
- Complete Liquid theme: layouts, templates, sections, snippets
- Theme settings schema so merchants customise without code
- Product, collection, cart and page templates
- Shopify CLI setup instructions included with the output
- Full code ownership — edit, version and extend the theme freely

Build the complete working project with its routes, data model and interactions. For saved or private data, implement persistence, authentication and server-side permissions. Keep API credentials on the server. For external services, document the required setup and use test mode until real accounts are connected. Do not present a simulated integration as a completed live connection.

Make the interface responsive, with accessible labels, keyboard navigation and visible focus. Include loading, empty, validation and error states. Use clearly labelled sample data, never invented customer testimonials or results. Choose a visual direction suited to this project and keep typography, spacing and controls consistent. Explain how to run, test, export and deploy the source.

Verify this end-to-end flow:
Install in a development store, edit sections in the theme editor and add a product variant to the cart. Check mobile navigation and unavailable variants.