Scaffold Svelte frontend and browser test matrix

Establish the TypeScript 7, Oxlint, Vitest, and Playwright workspace with an isolated Svelte diagnostics compatibility boundary.

web/vitest.browser.config.ts

@@ -0,0 +1,18 @@
+import { svelte } from '@sveltejs/vite-plugin-svelte'
+import { playwright } from '@vitest/browser-playwright'
+import { defineProject } from 'vitest/config'
+
+export default defineProject({
+  plugins: [svelte()],
+  test: {
+    name: 'component',
+    include: ['src/**/*.browser.test.ts'],
+    setupFiles: ['vitest-browser-svelte'],
+    browser: {
+      enabled: true,
+      headless: true,
+      provider: playwright(),
+      instances: [{ browser: 'chromium' }],
+    },
+  },
+})