Include the net's traces as conductors alongside zone fills

Straight tracks become capsule outline polygons (rectangle +
semicircular caps), arc tracks annular bands with end caps, both
tessellated to the same sagitta tolerance as zone-fill arcs; they merge
into the per-layer copper next to the fills, so rasterization, via
stitching, the solver and the plots handle them unchanged. Trace-only
layers and trace-only nets now qualify as candidates. Dialog checkbox
(on by default, INCLUDE_TRACKS) toggles them per run.

Hole-less polygons (every track outline) now paint the layer mask
directly instead of allocating a full-frame temporary each.

Tests: exact N-cell chain on a rasterized capsule, analytic annular-
sector convergence for an arc trace, capsule/arc-band outline geometry
invariants, collinear-arc degradation, and fill+trace union solve.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

fill_resistance/dialog.py

@@ -35,6 +35,7 @@ class Selection:
     contact_model: str = "uniform"
     include_buildup: bool = False
     extra_cu_um: float = 0.0
+    include_tracks: bool = True
 
 
 class _Dialog(QDialog):
@@ -59,6 +60,11 @@ class _Dialog(QDialog):
         self.layer_list.setMaximumHeight(120)
         form.addRow("Layers:", self.layer_list)
 
+        self.tracks_check = QCheckBox("include the net's traces "
+                                      "(tracks + arcs)")
+        self.tracks_check.setChecked(config.INCLUDE_TRACKS)
+        form.addRow("Conductors:", self.tracks_check)
+
         self.contact1_box = QComboBox()
         self.contact2_box = QComboBox()
         form.addRow(f"V+ ({e1_label}):", self.contact1_box)
@@ -199,7 +205,8 @@ class _Dialog(QDialog):
                          freq_hz=freq,
                          contact_model=self.model_box.currentData(),
                          include_buildup=self.buildup_check.isChecked(),
-                         extra_cu_um=extra_cu)
+                         extra_cu_um=extra_cu,
+                         include_tracks=self.tracks_check.isChecked())
 
     def _try_accept(self) -> None:
         try: