Function execute_charstring 

pub fn execute_charstring(
    charstring: &[u8],
    subrs: &[Vec<u8>],
    len_iv: usize,
    width_only: bool,
) -> Result<CharstringResult, String>

Execute a Type 1 charstring and produce path segments + width.

If width_only is true, path operations are skipped — only width is extracted. If cs_lookup is provided, seac (composite characters) can look up component charstrings.