ci(e2e): make backend stubs embeddable and keep vitest scoped

The dashboard embed pattern ignores hidden-only dist directories, so the CI backend stub must create visible index.html files. Keep the README in sync and exclude Playwright specs from Vitest so npm run test remains a unit-test command.

Co-authored-by: naiba/CloudCode <hi+cloudcode@nai.ba>

Co-authored-by: cloudcode <cloudcode@users.noreply.github.com>

vitest.config.ts

@@ -7,6 +7,7 @@ export default mergeConfig(
     defineConfig({
         test: {
             environment: "jsdom",
+            exclude: ["tests/e2e/**", "node_modules/**", "dist/**"],
             globals: true,
             setupFiles: ["./src/test/setup.ts"],
         },