Improve consistency and organization of examples for AI learning

- Add `.gitignore` files to all 19 examples (`node_modules/`, `dist/`)
- Replace custom `log` objects with standard `console` methods
- Add `ontoolcancelled` handler to all `basic-server-*` examples
- Add host styling integration (`applyDocumentTheme`, `applyHostFonts`,
  `applyHostStyleVariables`) to non-React `basic-server-*` examples
- Add section headers for better code organization in feature examples
- Update READMEs with Build System section explaining single-file
  bundling

These changes make examples more consistent and easier to adapt.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

examples/basic-server-react/README.md

@@ -30,3 +30,7 @@ npm run dev
 1. The server registers a `get-time` tool with metadata linking it to a UI HTML resource (`ui://get-time/mcp-app.html`).
 2. When the tool is invoked, the Host renders the UI from the resource.
 3. The UI uses the MCP App SDK API to communicate with the host and call server tools.
+
+## Build System
+
+This example bundles into a single HTML file using Vite with `vite-plugin-singlefile` — see [`vite.config.ts`](vite.config.ts). This allows all UI content to be served as a single MCP resource. Alternatively, MCP apps can load external resources by defining [`_meta.ui.csp.resourceDomains`](https://modelcontextprotocol.github.io/ext-apps/api/interfaces/app.McpUiResourceCsp.html#resourcedomains) in the UI resource metadata.