Function import_bundle_str 

pub fn import_bundle_str(
    src: &str,
    link: &dyn LinkRegistry,
) -> Result<ImportedProvider, FkcError>

Parse + validate a single bundle markdown file’s bytes into an ImportedProvider. Pure: no I/O of its own (tests pass &str).

parse_file → lower_file(.., link) → assemble. Every failure is a typed FkcError; never panics.