Route with copper zones, and let vias into no-tracks areas

freeroute ignored the DSN's planes (KiCad's zones), so it never knew that
pads in a pour are joined by it. On the rc4 power stage those pads sit
inside "keep router off" areas as well, and every connection to them was
dropped without a word.

- Read (plane <net> <shape>) and put each zone on the board as a
  ConductionArea of its net. Zones are not obstacles: KiCad refills them
  around other nets' copper.
- The grid groups each net's pads and zone pieces that copper already
  joins (a pad in a zone, two zones sharing a pad) and routes only between
  groups. A connection may end on a zone by a via inside its copper, or by
  a track where tracks are allowed.
- wire_keepout now blocks traces only, as KiCad's "no tracks" rule area
  does; via_keepout only vias; keepout both, in the grid and in the exact
  verifier.

rc4 power stage, exact engine, resolution 2: 2 unconnected, down from 8
(FreeRouting JAR: 12), no DRC errors.

src/freeroute/board/build.py

@@ -31,7 +31,7 @@ from freeroute.geometry.polygon_shape import PolygonShape
 
 from .board import BasicBoard
 from .clearance import ClearanceMatrix
-from .items import ObstacleArea, Pin
+from .items import ConductionArea, ObstacleArea, Pin
 from .layer import Layer, LayerStructure
 from .net import Nets
 from .transform import CoordinateTransform
@@ -55,6 +55,7 @@ def build_board(dsn: DsnBoard) -> BasicBoard:
     _insert_pins(dsn, board, transform, terminal_to_net)
     _insert_keepouts(dsn, board, transform)
     _insert_image_keepouts(dsn, board, transform)
+    _insert_zones(dsn, board, transform, nets)
     return board
 
 
@@ -330,6 +331,8 @@ def _insert_keepouts(dsn: DsnBoard, board: BasicBoard, transform: CoordinateTran
                     name=keepout.area.name,
                     layer=layer_index,
                     tiles=tiles,
+                    blocks_wires=keepout.kind != "via_keepout",
+                    blocks_vias=keepout.kind != "wire_keepout",
                 )
             )
 
@@ -402,13 +405,17 @@ def _insert_image_keepouts(dsn: DsnBoard, board: BasicBoard, transform: Coordina
         image = images.get(placement.lib_name)
         if image is None:
             continue
-        areas = [*image.keepouts, *image.via_keepouts, *image.wire_keepouts]
+        areas = [
+            *((a, True, True) for a in image.keepouts),
+            *((a, False, True) for a in image.via_keepouts),
+            *((a, True, False) for a in image.wire_keepouts),
+        ]
         if not areas:
             continue
         for place in placement.places:
             if place.x is None or place.y is None:
                 continue
-            for area in areas:
+            for area, blocks_wires, blocks_vias in areas:
                 border = area.border
                 if border is None:
                     continue
@@ -423,7 +430,12 @@ def _insert_image_keepouts(dsn: DsnBoard, board: BasicBoard, transform: Coordina
                     top, bottom = min(signal_layers), max(signal_layers)
                     layers = [top + bottom - layer for layer in layers]
                 for layer_index in layers:
-                    board.insert(ObstacleArea(name=area.name, layer=layer_index, tiles=tiles))
+                    board.insert(
+                        ObstacleArea(
+                            name=area.name, layer=layer_index, tiles=tiles,
+                            blocks_wires=blocks_wires, blocks_vias=blocks_vias,
+                        )
+                    )
 
 
 def _placed_area_tiles(shape: Shape, place, transform: CoordinateTransform) -> list:
@@ -447,3 +459,29 @@ def _placed_area_tiles(shape: Shape, place, transform: CoordinateTransform) -> l
     if len(pts) < 3:
         return []
     return [tile for tile in PolygonShape(pts).split_to_convex() if not tile.is_empty()]
+
+
+def _insert_zones(dsn: DsnBoard, board: BasicBoard, transform: CoordinateTransform, nets) -> None:
+    """Each DSN plane as a ConductionArea of its net on its layer."""
+    layer_no = {layer.name: i for i, layer in enumerate(dsn.layers)}
+    numbers = {net.name: net.net_number for net in nets}
+    for plane in dsn.planes:
+        shape = plane.shape
+        if plane.net not in numbers or shape.layer not in layer_no:
+            continue
+        if not isinstance(shape, (Polygon, Path)):
+            continue
+        c = shape.coords
+        pts = [transform.dsn_to_board_point(c[i], c[i + 1]) for i in range(0, len(c) - 1, 2)]
+        if len(pts) < 3:
+            continue
+        polygon = PolygonShape(pts)
+        tiles = [t for t in polygon.split_to_convex() if not t.is_empty()]
+        if not tiles:
+            continue
+        board.insert(
+            ConductionArea(
+                net_nos=[numbers[plane.net]], name=plane.net, layer=layer_no[shape.layer],
+                tiles=tiles, polygon=polygon, blocks_wires=False, blocks_vias=False,
+            )
+        )