Barrel contacts for vias/THT pads; configurable cap-drill threshold

- Selected vias and through-hole pads inject at the drill-wall ring on
  every spanned layer (both contact models), not the whole pad face,
  so the pad/pour spreading resistance is part of the result. Vias are
  now selectable as contacts.
- Soldered THT joints: the hole is modeled solder-filled (core in
  parallel with the plating, also for stitching THT barrels) and the
  pad face carries an average-thickness solder coat over the modeled
  copper (SOLDER_THICKNESS_UM).
- Vias with drills above a configurable threshold (dialog field,
  default CAP_MAX_DRILL_MM = 0.5) keep open mouths even with capping
  selected - the fab caps only small vias.
- Geometry dump schema v6: electrode barrel fields, cap_max_drill_nm.
- Verified against R = rho/(pi t)*acosh(d/2a) for two circular contacts
  on a sheet (+2.6% at h = 0.15 mm, a = 1 mm; uniform model above the
  equipotential one as required by the contact bracket).

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

fill_resistance/main.py

@@ -33,7 +33,7 @@ def main() -> None:
         try:
             kicad, board = board_io.connect()
             stackup = board_io.get_stackup_info(board)
-            es1, es2, net_hint = board_io.get_electrodes(board)
+            es1, es2, net_hint = board_io.get_electrodes(board, stackup)
             if board_io.any_zone_unfilled(board) or config.ALWAYS_REFILL:
                 board_io.refill(board)
             fills = board_io.gather_net_fills(board)
@@ -95,7 +95,8 @@ def main() -> None:
                 buildups=(buildups if selection.include_buildup else None),
                 extra_cu_um=selection.extra_cu_um,
                 tracks=(tracks if selection.include_tracks else None),
-                vias_capped=selection.vias_capped)
+                vias_capped=selection.vias_capped,
+                cap_max_drill_mm=selection.cap_max_drill_mm)
             outdir = report.make_output_dir(board_io.board_dir(board))
         except ApiError as e:
             raise UserFacingError(f"KiCad API error: {e}")