fix(zoom): include 3D solid meshes in model-space extents

ZOOM EXTENTS / auto-fit derived the drawing bounds from wire AABBs and
tessellated key-vertices only. 3D solids (Solid3D/Region/Body) render as
meshes with an empty wire path, so they contributed nothing and a
drawing containing only solids zoomed to nothing. Fold each mesh's
offset-relative XY AABB into the extents on both the wire-cache and
tessellate-fallback paths.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/scene/mod.rs

@@ -2652,6 +2652,16 @@ impl Scene {
                             any = true;
                         }
                     }
+                    // 3D solids render as meshes, not wires, so fold their
+                    // XY AABBs in too — otherwise ZOOM EXTENTS ignores them.
+                    for set in self.meshes.values() {
+                        let [ax, ay, bx, by] = set.world_aabb;
+                        if ax.is_finite() && bx.is_finite() {
+                            min = min.min(glam::Vec3::new(ax + ox as f32, ay + oy as f32, 0.0));
+                            max = max.max(glam::Vec3::new(bx + ox as f32, by + oy as f32, 0.0));
+                            any = true;
+                        }
+                    }
                     return if any { Some((min, max)) } else { None };
                 }
             }
@@ -2690,6 +2700,15 @@ impl Scene {
                 }
             }
         }
+        // Same mesh inclusion for the tessellate fallback path.
+        for set in self.meshes.values() {
+            let [ax, ay, bx, by] = set.world_aabb;
+            if ax.is_finite() && bx.is_finite() {
+                min = min.min(glam::Vec3::new(ax + ox as f32, ay + oy as f32, oz));
+                max = max.max(glam::Vec3::new(bx + ox as f32, by + oy as f32, oz));
+                any = true;
+            }
+        }
         if any {
             return Some((min, max));
         }