Function visit_lcs_equal_runs 

pub fn visit_lcs_equal_runs<E>(
    old_bytes: &[u8],
    new_bytes: &[u8],
    scratch: &mut [u8],
    budget: &mut ResourceBudget,
    visit: impl FnMut(EqualRun) -> Result<(), E>,
) -> LcsVisitResult<E>

Visit equal index ranges in deterministic Myers order.

Line scanning writes offsets into scratch. The algorithm never builds Vec<String> inputs or a Vec<(usize, usize)> match set. Work is the number of Myers line comparisons actually performed. A visitor Err stops promptly.