I'm not sure I understand how to push the PWA theme into production.
So you have to install the PWA theme, just like a regular theme and this provides the app shell
Then you install the pwa-studio with the Venia theme, this give you a DEV server that you can code and test on
When you're ready, you build this app and push it to the PWA theme?
When you call the url www.yourmagentostore.com
The PWA theme sends the app shell?
Is this right?
PWA magento developing is a completely independent of theming in magento 2. Your magento store can run both PWA and the theme based store side by side. The PWA store is a separate server that communicates with your magento store through REST calls and GRAPHQL calls.
The PWA studio has set of tools and a sample implementation of store namely Venia Concept. With PWA studio you have necessary React components like Routing, Page, lists, menu bar etc. and application setup. The sample Venia Concept is for your reference to build your store.
The production environment has two servers one with default magento store that you may or may not want to publish and another PWA server that you publish.
Finally The PWA is a complete app and not a theme like luma or blank in magento. You cannot extend from a base theme or parent theme like luma
How a visitor's device will detect the website visited is available as PWA?