Proxy mode

I run Vite as proxy of built-in php server:
```js
import {defineConfig} from 'vite';
import fullReload from 'vite-plugin-full-reload';

export default defineConfig({
server: {
proxy: {
'/': 'http://localhost:8080'
}
},
plugins: [
fullReload('*.php')
],
});

```

The problem: when I update PHP file, I see «page reload» message in the terminal, but no page reload happens.

Start by reproducing the issue with the shown Vite server.proxy configuration, the built-in PHP server, and fullReload('*.php'). Trace the reload behavior when a PHP file changes while the page is served through the proxy. Done means the browser reloads after the terminal reports the page reload.

Written by the indexing model from the issue text.