Module loader 

Load docs from an rtb_assets::Assets tree into the (Index, HashMap<path, body>) shape that crate::DocsBrowser and crate::DocsServer consume.

The convention is:

• <root>/_index.yaml — optional, parsed via crate::index::parse_index.
• Every .md file under <root>/ — body is loaded into the returned HashMap keyed on its <root>-relative path. When no _index.yaml is present, crate::index::scan_index derives one from the discovered pages.

_index.yaml follows last-wins shadowing, not a deep merge: the highest-priority layer’s file replaces the embedded one wholesale, as rtb_assets::Assets::open_text does for any other path.

Functions

load_docs

Walk <root>/ for .md files + an optional _index.yaml. Returns the parsed Index and a path -> body map.