Public Download File

Public source-download endpoint for the chat file-card 'Open' link.

Mirrors public_preview_file for resolution (UUID file id or legacy cross-user path) but always returns Content-Disposition: attachment; filename="..." so the browser saves under the source filename instead of trying to render the bytes inline. Used by InlineFilePreview 'Open' affordances that render as plain <a href>: those clicks — plus middle- click / right-click "open in new tab" / "copy link" — don't carry the frontend's bearer token, so the auth'd /api/files/download/{file_id} route would 401 every plain browser navigation.

The file_id is the only required capability, matching the existing public/preview contract. relative_path is intentionally NOT supported: 'Open' always targets the registered source artifact, never a sub-path inside it.