create-example

Checklist

1. Create the app folder with src/, data/state.json when SSR state is needed, package.json, tsconfig.json, and a concise demo.toml.
2. Use the shared theme for example UI: add @microsoft/webui-examples-theme, pass --theme=@microsoft/webui-examples-theme, and inject /*{{{tokens.light}}}*/ plus /*{{{tokens.dark}}}*/ in the entry template.
3. Keep package.json scripts consistent: build, start:client, start:server, start, test, and test:update-snapshots when Playwright applies.
4. Add Playwright coverage in tests/ and a playwright.config.ts using the app's fixed dev port. Prefer behavior tests over screenshots unless the UI is the point.
5. Register the app in xtask/src/e2e.rs when it has Playwright tests. Use pre_script: Some("build") for custom build pipelines that the generic esbuild step cannot reproduce.
6. Add demo.toml, copy the app into examples/demo/Dockerfile, and list it in examples/README.md.
7. Run the focused app test, then cargo xtask check.