Function get_route_templates 

pub fn get_route_templates(
    protocol: &WebUIProtocol,
    entry_id: &str,
    inventory_hex: &str,
) -> (Vec<(String, String)>, String)

Get the f-template HTML strings needed for a route that the client doesn’t already have.

Walks the fragment graph from entry_id, identifies needed components (not in the client’s inventory), and returns their f-template HTML from the protocol’s components map.

Returns (templates: Vec<(name, html)>, updated_inventory_hex).