--smooth: no 45-degree leg shorter than two track widths

A short diagonal at a wire's end is a kink beside its pad, and the pour
refilled round it left a copper sliver (KiCad copper_sliver) on the
TerraHawk lights node. Small offsets now stay square jogs; chamfers get
the same floor.

tests/route/test_smooth.py

@@ -146,3 +146,17 @@ def test_a_detour_with_nothing_in_its_way_is_straightened():
     assert _points(result.nets[0].wires[0]) == [(22000, -2000), (22000, -22000)]
     assert (report.before.right_angles, report.after.right_angles) == (2, 0)
     assert verify_result(dsn, result).clean
+
+
+def test_a_jog_too_small_for_a_long_diagonal_stays_square():
+    # a 0.1 mm jog halfway: its 45-degree leg would be shorter than two track
+    # widths, a kink beside the copper that leaves pour slivers
+    dsn = parse_dsn(_board(extra_places="(place A3 2100 -22000 front 0)").replace(
+        "(pins A1-1 A2-1)", "(pins A1-1 A3-1)"))
+    wire = [(2000, -2000), (2000, -12000), (2100, -12000), (2100, -22000)]
+    result = _result(_wire(wire))
+    smooth(dsn, result)
+    pts = _points(result.nets[0].wires[0])
+    for a, b in zip(pts, pts[1:], strict=False):
+        if a[0] != b[0] and a[1] != b[1]:
+            assert (b[0] - a[0]) ** 2 + (b[1] - a[1]) ** 2 >= (2 * 200) ** 2