fix(ci): exclude Playwright e2e specs from Vitest run

The Phase 3 Playwright harness stub landed
web/src/__tests__/e2e/smoke.spec.ts using @playwright/test's
test.describe(). Vitest's default include glob
('**/*.{test,spec}.{js,...}') matches that file and tries to
execute it under jsdom, but test.describe() from Playwright
throws:

    Error: Playwright Test did not expect test.describe() to be
    called here.

The Frontend Build CI job (npm run test → vitest run) hits this
on every push.

Fix: extend the Vitest exclude list to skip src/__tests__/e2e/**.
Playwright still runs them via 'npm run e2e' against
web/playwright.config.ts (testDir './src/__tests__/e2e').

Verified locally that fast-glob matches the file at that pattern.
configDefaults imported from 'vitest/config' preserves Vitest's
own default excludes (node_modules + .git) alongside the
addition.

web/vite.config.ts

@@ -1,4 +1,5 @@
 import { defineConfig } from 'vite'
+import { configDefaults } from 'vitest/config'
 import react from '@vitejs/plugin-react'
 
 // C-1 closure (cat-u-vite_dev_proxy_plaintext_drift): pre-C-1 the dev
@@ -25,5 +26,11 @@ export default defineConfig({
     globals: true,
     environment: 'jsdom',
     setupFiles: ['./src/test/setup.ts'],
+    // Exclude Playwright e2e specs from the Vitest run. The harness in
+    // src/__tests__/e2e/ uses @playwright/test's test.describe(), which
+    // throws "did not expect test.describe() to be called here" under
+    // Vitest. Playwright runs them via `npm run e2e` against
+    // web/playwright.config.ts (testDir: './src/__tests__/e2e').
+    exclude: [...configDefaults.exclude, 'src/__tests__/e2e/**'],
   },
 })