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/board/build.py

@@ -27,6 +27,7 @@ import math
 from freeroute.dsn.model import DsnBoard
 from freeroute.dsn.shapes import Circle, Path, Polygon, Rectangle, Shape
 from freeroute.geometry import FloatPoint, IntBox, IntPoint, IntVector, Simplex
+from freeroute.geometry.polygon_shape import PolygonShape
 
 from .board import BasicBoard
 from .clearance import ClearanceMatrix
@@ -219,11 +220,14 @@ def _insert_keepouts(dsn: DsnBoard, board: BasicBoard, transform: CoordinateTran
     signal_layers = [i for i, layer in enumerate(dsn.layers) if layer.is_signal]
 
     for keepout in dsn.keepouts:
+        # A place_keepout only restricts where parts go, not copper.
+        if keepout.kind == "place_keepout":
+            continue
         area = keepout.area
         if area is None or area.border is None:
             continue
-        tile = _area_border_tile(area.border, transform)
-        if tile is None:
+        tiles = _area_border_tiles(area.border, transform)
+        if not tiles:
             continue
         border_layer = area.border.layer
         if border_layer in ("signal", "pcb"):
@@ -237,11 +241,36 @@ def _insert_keepouts(dsn: DsnBoard, board: BasicBoard, transform: CoordinateTran
                 ObstacleArea(
                     name=keepout.area.name,
                     layer=layer_index,
-                    tiles=[tile],
+                    tiles=tiles,
                 )
             )
 
 
+def _area_border_tiles(shape: Shape, transform: CoordinateTransform) -> list:
+    """Convex board tiles covering a keepout border shape.
+
+    Polygons are split into convex pieces rather than wrapped in one convex
+    tile: KiCad exports a rule area with a hole (a no-track ring along the
+    board edge, say) as a single keyhole polygon, and its convex hull is the
+    whole board.
+    """
+    if isinstance(shape, (Polygon, Path)):
+        coords = shape.coords
+        pts = [
+            IntPoint(
+                round(transform.dsn_to_board(coords[i])),
+                round(transform.dsn_to_board(coords[i + 1])),
+            )
+            for i in range(0, len(coords) - 1, 2)
+        ]
+        if len(pts) >= 3:
+            pieces = [t for t in PolygonShape(pts).split_to_convex() if not t.is_empty()]
+            if pieces:
+                return pieces
+    tile = _area_border_tile(shape, transform)
+    return [tile] if tile is not None else []
+
+
 def _area_border_tile(shape: Shape, transform: CoordinateTransform):
     """Convert an absolute-coordinate keepout border shape to one board tile."""
     if isinstance(shape, Rectangle):