fix: install VS Code from Microsoft's direct download endpoint instead of apt repo

The apt repo at packages.microsoft.com/repos/vscode does not publish amd64
and arm64 .deb packages atomically, so the arm64 build in CI could pick up
an older VS Code version than amd64 when both platforms build in the same run.

Switch to downloading the .deb directly from
update.code.visualstudio.com/latest/linux-deb-{arch}/stable, the canonical
"always latest" endpoint, and resolve dependencies via apt-get install -f.

Also add an explicit docker/setup-qemu-action step to the workflow so arm64
emulation is version-pinned rather than relying on the runner's default
binfmt registration.

.github/workflows/main-workflow.yml

@@ -11,6 +11,9 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v2
 
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v1