Function split_block_with 

pub fn split_block_with(
    text: &str,
    begin: &str,
    end: &str,
) -> Result<(String, Option<String>), MarkerError>

Split a host text into its lines outside a marked region and the region.

The pre-commit split_block is this with the pre-commit markers; the AGENTS.md block uses its own pair.

Errors

MarkerError::Malformed when the marker counts disagree or a second region appears; MarkerError::OutOfOrder when the end precedes the begin.