Function parse_wkt_linestring 

pub fn parse_wkt_linestring(
    wkt: &str,
) -> Result<LineString<f64>, ProjectionError>

Parse a LINESTRING(...) WKT into a [LineString<f64>].

Inline parser to avoid pulling a wkt-crate dependency. Accepts upper or lower-case keyword and any whitespace between tokens. Does NOT handle Z/M.