Move Vite build-file copying into scripts

Keep the Node.js build helper and its tests in the build-script directory
recognised by Community review. Update the Vite import and unit CI path
filters while preserving the copy behaviour and release artefacts.

.github/workflows/unit-ci.yml

@@ -13,6 +13,7 @@ on:
       - 'src/**'
       - 'test/**'
       - '_tools/**'
+      - 'scripts/**'
       - 'package.json'
       - 'package-lock.json'
       - 'tsconfig.json'
@@ -51,6 +52,7 @@ on:
       - 'src/**'
       - 'test/**'
       - '_tools/**'
+      - 'scripts/**'
       - 'package.json'
       - 'package-lock.json'
       - 'tsconfig.json'