Function read_architect_source_export 

pub fn read_architect_source_export(
    config: &DbBackendConfig,
    adapter: &dyn DatabaseOperations,
    schema: &AppSchema,
    export_id: &str,
    export_root: &Path,
) -> Result<ArchitectSourceExportDownload, AgentErrorKind>

Verifies one unexpired source export bundle before handing its local path to a caller.