Initial scaffold: spec, architecture playbook, and M0 skeleton

vite.config.ts

@@ -0,0 +1,41 @@
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+import { VitePWA } from 'vite-plugin-pwa';
+import { readFileSync } from 'node:fs';
+import { fileURLToPath } from 'node:url';
+
+const pkg = JSON.parse(readFileSync(new URL('./package.json', import.meta.url), 'utf-8'));
+
+export default defineConfig({
+  resolve: {
+    alias: {
+      '@': fileURLToPath(new URL('./src', import.meta.url)),
+      '@core': fileURLToPath(new URL('./src/core', import.meta.url)),
+    },
+  },
+  define: {
+    __APP_VERSION__: JSON.stringify(pkg.version),
+  },
+  plugins: [
+    react(),
+    VitePWA({
+      registerType: 'prompt',
+      includeAssets: ['favicon.svg'],
+      manifest: {
+        name: 'Astrolabe',
+        short_name: 'Astrolabe',
+        description: 'A browser-based snippet manager for Vega-Lite visualizations.',
+        theme_color: '#1a1a2e',
+        background_color: '#ffffff',
+        display: 'standalone',
+        icons: [],
+      },
+    }),
+  ],
+  // Vitest config (shares this file)
+  test: {
+    globals: true,
+    environment: 'happy-dom',
+    include: ['src/**/*.test.{ts,tsx}'],
+  },
+} as Parameters<typeof defineConfig>[0]);