CI/CD Hyvä Installation
The app/etc/hyva-themes.json file contains the information which modules should be included when generating a themes styles.css file.
More information on the automatic tailwind.config.js merge process can be found at the "Module tailwind.config.js merging" documentation.
Hyvä 1.1.14 and newer
The app/etc/hyva-themes.json file used during the compilation of a themes styles.css file is generated automatically after one of the commands 
bin/magento setup:installbin/magento setup:upgradebin/magento module:enablebin/magento module:disable
This will usually be enough to take care of all scenarios automatically, so you don't have to worry about it during CI/CD builds.
Hyvä 1.1.13 and older
The app/etc/hyva-themes.json file used during the compilation of a themes styles.css file is generated automatically after one of the commands
bin/magento setup:upgradebin/magento module:enablebin/magento module:disable
However, in Hyvä versions 1.1.13 and older, the bin/magento setup:install command does not cause the hyva-themes.json file to be created.
Because of this, if you run bin/magento setup:install while the Hyvä packages are already present, be sure to run the command bin/magento hyva:config:generate afterwards, before you generate the styles.css during the build.
This will usually be the case during CI/CD builds.