Function run_multi_source_demo 

pub fn run_multi_source_demo<R, Resolve, Build, I>(
    args_iter: I,
    resolve_roots: Resolve,
    build_sources: Build,
) -> Result<(), Box<dyn Error>>
where
    Resolve: FnOnce(Vec<String>) -> Result<R, Box<dyn Error>>,
    Build: FnOnce(&R) -> Vec<Box<dyn DataSource + 'static>>,
    I: Iterator<Item = String>,

Run the multi-source demo CLI with injectable root resolution/source builders.

build_sources is construction-only. Source sampler configuration is owned by sampler registration (TripletSampler::register_source).