Function open_self_described_reader 

pub async fn open_self_described_reader(
    scheduler: FileScheduler,
    decoder_plugins: Arc<DecoderPlugins>,
    cache: &LanceCache,
    options: FileReaderOptions,
) -> Result<OpenedFileReader>

Open a self-described file and dispatch to the matching reader.

The current-format reader’s optimistic tail read is also used for exact version detection, so current files do not pay for a separate footer probe.