Function fleet_pythagorean48_encode 

#[unsafe(no_mangle)]
pub extern "C" fn fleet_pythagorean48_encode(x: f64, y: f64) -> i32

Quantize a 2D angle (from x, y components) into one of 48 discrete directions.

Each direction spans 7.5° (360°/48). Returns an integer in [0, 47] where 0 corresponds to the positive x-axis.

Returns 0 if (x, y) is the zero vector.