feat: add SwiftUI macOS main window demo with CI

scripts/generate-xcodeproj.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+set -euo pipefail
+if ! command -v xcodegen >/dev/null 2>&1; then
+  echo "xcodegen not found. Install with: brew install xcodegen" >&2
+  exit 1
+fi
+cd "$(dirname "$0")/.."
+xcodegen generate