Prepare a dedicated `.next/electron-standalone` bundle before
running electron-builder so desktop packaging operates on a stable,
Electron-specific server payload.
This also adds a preflight that rejects standalone bundles whose
top-level `node_modules` is a symlink, because electron-builder
preserves `extraResources` symlinks and would otherwise ship an app
that depends on the build machine at runtime.
Kfir Amar
22f9e6f4c0