Function paper_source_bundle 

pub async fn paper_source_bundle(
    base: &Url,
    id: &ArxivId,
    filter: BundleFilter,
    ctx: &FetchContext,
) -> Result<Vec<SourceFile>, FetchError>

Fetch the arXiv source bundle (or figures only) for id.

Tier-1 OA, always-on (ADR-0034 D1). Performs the SAME single /src/<id> request as paper_tex_source and returns the selected files in memory; the caller writes them to disk. Every returned path is sanitised (ADR-0034 D3). Not cached (ADR-0034 D5).

Errors

• FetchError::Http — transport / status failure.
• FetchError::TextUnavailable — PDF-only / single-file submission, or no matching files (e.g. --figures-only on a figure-less submission).
• FetchError::SourceSchema — URL construction or gzip/tar parse error.
• FetchError::Log — provenance append failed (fail-closed).