Function write_sr 

pub fn write_sr<W: Write>(
    w: &mut W,
    num_vars: usize,
    original: &[Vec<Lit>],
    steps: &[ProofStep],
) -> Result<(), EmitError>

Streaming core of emit_sr: write the SR proof into any core::fmt::Write sink rather than a String, so its serialized size can be measured through a capped SizeSink in O(1) memory (and bail early on a pathological proof) instead of building the whole text. Byte-for-byte identical to emit_sr; the String-backed wrapper above simply cannot hit EmitError::SizeCapExceeded.