Blender Grease Pencil - traps

Every trap measured headless on Blender 5.1.2 (blender-round3 probes, 2026-11-08). Blender 4.3 replaced Grease Pencil with GPv3; the 2.8-4.2 API is GONE, not deprecated. Still valid: bpy.data.grease_pencils.new(), object type 'GREASEPENCIL', gp.layers.new(name), layer.frames.new(n), layer.blend_mode, onion skinning, bpy.data.materials.create_gpencil_data(mat), stroke.material_index.

1. Strokes live on the frame's drawing. Wrong: frame.strokes.new() (AttributeError: 'GreasePencilFrame' has no attribute 'strokes'). Right: d = layer.frames.new(1).drawing; d.add_strokes([n_points]); s = d.strokes[-1]. Verify: [(f.frame_number, [len(s.points) for s in f.drawing.strokes]) for f in layer.frames].

2. Points are added on the stroke and positioned with position. Wrong: stroke.points.add(count=3), point.co. Right: stroke.add_points(n) (appends), point.position = (x, y, z) (object space). Verify: read p.position back for every point.

3. Thickness is per-point radius. Wrong: stroke.line_width = 10 (AttributeError). Right: point.radius in world units; new points default to 0.01, so set it explicitly. Verify: read p.radius back.