Route past round pads by their outline, not their bounding square

A circle pad was its bounding box in both the grid and the exact check, so a
4 mm mounting hole's square corners refused legal routes 0.8 mm clear of the
real copper. It is now a 16-sided polygon whose sides touch the circle, so
the router is never closer than KiCad measures. diagnose.py takes --seed.

bench/diagnose.py

@@ -185,7 +185,7 @@ def _flood(router: GridRouter, pin, net_no: int, conns) -> tuple[int, Counter]:
 
 def diagnose(
     dsn_text: str, edge_clearance_mm: float | None, resolution: int = 2, shove: bool = False,
-    access_cost: float = 0.0, hole_to_hole_mm: float = 0.25,
+    access_cost: float = 0.0, hole_to_hole_mm: float = 0.25, seed: int | None = None,
 ) -> dict:
     dsn = parse_dsn(dsn_text)
     names = {i + 1: n.name for i, n in enumerate(dsn.nets)}
@@ -201,6 +201,7 @@ def diagnose(
         resolution=resolution,
         shove=shove,
         access_cost=access_cost,
+        seed=seed,
         # the product's configuration: net-class widths and hole spacing
         net_widths=_net_widths_board(dsn, scale),
         via_drill=_via_drill_board(dsn, scale),
@@ -276,12 +277,13 @@ def main(argv: list[str] | None = None) -> int:
     ap.add_argument("--grid-resolution", type=int, default=2, metavar="K")
     ap.add_argument("--shove", action="store_true", help="as mckicad routes")
     ap.add_argument("--access-cost", type=float, default=0.0)
+    ap.add_argument("--seed", type=int, help="route in this shuffled order, as bench.py does")
     ap.add_argument("--hole-to-hole", type=float, default=0.25, metavar="MM")
     ap.add_argument("--json", type=Path, help="also write the full table here")
     args = ap.parse_args(argv)
 
     report = diagnose(args.dsn.read_text(), args.edge_clearance, args.grid_resolution, args.shove,
-                      args.access_cost, args.hole_to_hole)
+                      args.access_cost, args.hole_to_hole, args.seed)
     for row in report["failures"]:
         extra = ""
         for w in row.get("walled", []):