HtmlLivePreviewWrapper
Renders the live-preview HTML wrapper, which embeds a target document inside double-buffered iframes with scroll preservation, and subscribes to a Server-Sent Events reload stream.
The reload URL is built by concatenating endpointRoot with the endpoint name (reload).
Parameters
srcFile
URL or path used as the iframe's src
endpointRoot
path prefix concatenated with the endpoint name to form the SSE URL. Defaults to DEFAULT_ENDPOINT_ROOT (/); pass e.g. "../" to produce ../reload.