fn find_top_level_model(
body: &[u8],
) -> Result<Option<((usize, usize), String)>, SpliceError>Expand description
Locate the top-level "model" string value: its byte span
(excluding the quotes) and its content. Scans with a string/escape
state machine so a "model" that is only a nested key or a value
elsewhere is skipped.