/**
* HTML rewriter for the embedded-service reverse proxy.
*
* Rewrites an HTML document so that absolute-path URLs point through the
* OmniRoute proxy prefix instead of directly to the embedded service's port.
*
* What it does:
* - Inserts `` as the first child of ``.
* - Rewrites path-absolute URLs (starting with `/` but NOT `//`) in selected
* attributes: , ,