Add GitHub Actions CI for Windows portable build

.github/workflows/build.yml

@@ -0,0 +1,32 @@
+name: Build Windows
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: windows-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 24
+          cache: npm
+
+      - run: npm ci
+
+      - run: npx electron-builder --win portable
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: Helix-portable
+          path: dist/Helix*.exe
+          if-no-files-found: error