Please follow these steps :
- Run npm run dev : It will update clientlib-site and clientlib-dependencies and update ui.apps folder in file system.
- Deploy updated code to AEM. Command : mvn clean install -PautoInstallPackage
Once the code is installed , please check your changes under /apps/project/clientlibs/clientlib-site. If changes are not there probably then you need to check first step I mentioned above. The command npm run dev builds your CSS & JS files using webpack. You can refer the scripts section in package.json of ui.frontend module.
"dev": "webpack --env dev --config ./webpack.dev.js && clientlib --verbose",
If you see your changes in /apps/project/clientlibs and same clientlibs you are able to see getting loaded on page, then probably you need to clean cache of your browser to reflect latest changes.
Document : https://experienceleague.adobe.com/docs/experience-manager-core-components/using/developing/archetype/uifrontend.html?lang=en