Honour KiCad's keepouts: keyhole rings, wire_keepout, per-tile rasterizing

On the TerraHawk rc4 power stage every engine misread the board's rule areas:

- A no-track ring along the board edge arrives as one keyhole polygon, and
  keepout polygons were wrapped in a single convex tile, so the ring became
  the whole board. Split keepout polygons into convex pieces instead.
- The grid engine rasterized an area by its overall bounding box, which for
  that ring is again the whole board; it routed nothing. Rasterize per tile.
- "Keep router off" rule areas arrive as wire_keepout, which the reader did
  not know, so tracks ran through them (172 DRC items_not_allowed). Read it
  at board and image level. For now it blocks vias too, which is stricter
  than KiCad and cannot create a violation.
- place_keepout only restricts part placement; stop treating it as copper.

The oracle now runs the JAR headless; it was opening FreeRouting's GUI on
the desktop for every oracle test.

src/freeroute/dsn/reader.py

@@ -178,6 +178,11 @@ def _read_structure(node: SExp, board: DsnBoard) -> None:
             area = read_area(it)
             if area is not None:
                 board.keepouts.append(Keepout(area=area, kind="via_keepout"))
+        elif head == "wire_keepout":
+            # KiCad writes a "no tracks" rule area this way (vias allowed).
+            area = read_area(it)
+            if area is not None:
+                board.keepouts.append(Keepout(area=area, kind="wire_keepout"))
         elif head == "place_keepout":
             area = read_area(it)
             if area is not None:
@@ -285,6 +290,10 @@ def _read_image(node: SExp) -> Image | None:
             area = read_area(it)
             if area is not None:
                 image.via_keepouts.append(area)
+        elif head == "wire_keepout":
+            area = read_area(it)
+            if area is not None:
+                image.wire_keepouts.append(area)
         elif head == "place_keepout":
             area = read_area(it)
             if area is not None: