Function project_lit 

pub fn project_lit(
    vert: Vec3I16,
    normal: Vec3I16,
    material: (u8, u8, u8),
) -> ProjectedLit

Project a vertex AND compute its lit colour in one call.

Does RTPS on vert + NCCS on normal, with a per-vertex material RGB loaded into RGBC (data reg 6) to modulate the GTE’s lit output. Pass (128, 128, 128) as material for “unmodulated” behaviour – the lit colour comes through as the light rig + ambient dictate.

Prerequisites (caller’s responsibility, as with scene::project_vertex):

• Rotation matrix loaded (scene::load_rotation)
• Translation loaded (scene::load_translation)
• Projection plane / screen offset set (scene::set_projection_plane, scene::set_screen_offset)
• Light rig loaded (LightRig::load, with for_object applied so lights are in the same frame as the normal)