Function export_html_dataset 

pub fn export_html_dataset(
    connection: &mut PgConnection,
    corpus: &Corpus,
    service: &Service,
    severities: &[TaskStatus],
    group_by: GroupBy,
    max_archive_mb: Option<u64>,
    out_dir: &PathBuf,
    progress: impl FnMut(&str),
) -> Result<DatasetExportOutcome, String>

Export a corpus/service’s converted HTML into ZIP archives bucketed by GroupBy.

Reads existing result archives off the shared filesystem (no conversion is run); the DB is only queried for the matching task entry paths. progress is called with human-readable milestone lines (the CLI prints them; a future web/job caller can stream them). Resumable: an archive whose .zip already exists in out_dir is left untouched (matching the scripts’ resume behaviour).

Severities are taken in the given order; the canonical TaskStatus::to_key spelling is used throughout (no no-problem/no_problem ambiguity).