幂等键指纹的键排序改成具名比较函数

- src/components/image-editor/model3d-generation/Model3dGenerationSubmission.ts：canonicalizeModel3dRequestValue 里的嵌套三元比较器提成模块级 compareModel3dRequestEntryKeys，排序结果不变，只是不再嵌三元且不必每次递归重建比较器

验证：npx vitest run src/components/image-editor/model3d-generation（39 用例全绿）

src/components/image-editor/model3d-generation/Model3dGenerationSubmission.ts

@@ -164,6 +164,17 @@ export function resolveModel3dRequestKey({
   return `${nonce}-${fingerprintModel3dRequest(endpoint, body)}`;
 }
 
+/** 键排序只求稳定，不承载任何业务语义：同一份内容必须算出同一个键。 */
+function compareModel3dRequestEntryKeys(
+  [left]: [string, unknown],
+  [right]: [string, unknown],
+) {
+  if (left < right) {
+    return -1;
+  }
+  return left > right ? 1 : 0;
+}
+
 function canonicalizeModel3dRequestValue(value: unknown): unknown {
   if (Array.isArray(value)) {
     return value.map(canonicalizeModel3dRequestValue);
@@ -172,7 +183,7 @@ function canonicalizeModel3dRequestValue(value: unknown): unknown {
     return Object.fromEntries(
       Object.entries(value as Record<string, unknown>)
         .filter(([, entry]) => entry !== undefined)
-        .sort(([left], [right]) => (left < right ? -1 : left > right ? 1 : 0))
+        .sort(compareModel3dRequestEntryKeys)
         .map(([key, entry]) => [key, canonicalizeModel3dRequestValue(entry)]),
     );
   }