前端补上「分件 + 方形布线 / 智能低多边形」的互斥校验

- src/components/image-editor/model3d-generation/Model3dGenerationFormModel.ts：resolveModel3dGenerationParams 增加 generateParts 与 quad / smartLowPoly 的互斥判定，与 provider 的 validate_generation_options 对齐；此前纯几何档位下这两个开关仍可同开，前端能出价、提交后才被后端拒
- src/components/image-editor/model3d-generation/Model3dGenerationFormModel.test.ts：新增该组合被拒的用例

验证：npx vitest run src/components/image-editor/model3d-generation（40 用例全绿）

src/components/image-editor/model3d-generation/Model3dGenerationFormModel.test.ts

@@ -159,6 +159,27 @@ describe('resolveModel3dGenerationParams', () => {
       }).ok,
     ).toBe(false);
   });
+
+  it('分件不允许与方形布线 / 智能低多边形同时开，这是后端也会拒的组合', () => {
+    const conflictingSwitches: Array<{ quad: boolean; smartLowPoly: boolean }> =
+      [
+        { quad: true, smartLowPoly: false },
+        { quad: false, smartLowPoly: true },
+      ];
+    for (const switches of conflictingSwitches) {
+      expect(
+        resolveModel3dGenerationParams({
+          tier: 'geometry-only',
+          quad: switches.quad,
+          smartLowPoly: switches.smartLowPoly,
+          generateParts: true,
+        }),
+      ).toEqual({
+        ok: false,
+        reason: '分件生成不能与方形布线或智能低多边形同时使用',
+      });
+    }
+  });
 });
 
 describe('resolveModel3dAddOnKeys', () => {