added preset saving and heat transfer

draw_toroid.py

@@ -78,6 +78,7 @@ def draw_toroid(
     output_path: str = "toroid.png",
     dpi: int = 180,
     fig_size_mm: float = 180.0,
+    actual_fill: float | None = None,
 ) -> None:
     """
     Render a to-scale top-down cross-section of the transformer as a PNG.
@@ -110,9 +111,10 @@ def draw_toroid(
     ax.set_xlabel("mm", fontsize=8)
     ax.set_ylabel("mm", fontsize=8)
     ax.tick_params(labelsize=7)
+    fill_str = f"  fill={actual_fill*100:.1f}%" if actual_fill is not None else ""
     ax.set_title(
         f"Toroid cross-section  "
-        f"ID={ID:.1f} mm  OD={OD:.1f} mm  H={core.height_mm:.1f} mm",
+        f"ID={ID:.1f} mm  OD={OD:.1f} mm  H={core.height_mm:.1f} mm{fill_str}",
         fontsize=9, pad=6,
     )