fix: render wipeout fills after wire pass so they correctly mask wires

Previously wipeout solid fills were part of the hatch pass (pass 1),
drawn before wires (pass 5), so all wires appeared on top of the
wipeout. This fix moves wipeout fills into a dedicated pass 6 that
runs after wires, so the background-colored polygon correctly covers
the lines/text beneath it — matching AutoCAD behaviour.

- Scene.wipeout_models() separated from synced_hatch_models()
- Primitive.wipeout_hatches populated via wipeout_models()
- Pipeline.gpu_wipeouts + upload_wipeouts() + pass 6 after wires

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/scene/mod.rs

@@ -1249,15 +1249,18 @@ impl Scene {
             }
         }
 
-        // ── Wipeout solid fills ───────────────────────────────────────────────
-        // Wipeouts are rendered as background-colored filled polygons so that
-        // they mask hatch fills drawn earlier in the same pass.
-        // Wipeout fills are appended last so they render on top of other hatches.
+        models
+    }
+
+    /// Wipeout fill models — rendered in a separate pass AFTER wires so that
+    /// wipeouts correctly mask everything below them in the draw order.
+    pub(super) fn wipeout_models(&self) -> Vec<HatchModel> {
         let bg_color: [f32; 4] = if self.current_layout == "Model" {
             self.bg_color
         } else {
             self.paper_bg_color
         };
+        let mut models = Vec::new();
         for entity in self.document.entities() {
             let EntityType::Wipeout(wo) = entity else { continue };
             if entity.common().invisible {
@@ -1286,7 +1289,6 @@ impl Scene {
                 });
             }
         }
-
         models
     }