修复了2个bug

tests/seedream-layer-compositions.test.ts

@@ -1,7 +1,21 @@
 import { readFile } from "node:fs/promises";
 import { describe, expect, it } from "vitest";
+import { hasCompleteSeedreamLayerMetadata } from "@/lib/seedream/layer-composition";
 
 describe("Seedream layer composition persistence contract", () => {
+  it("only enables the editable layer project for complete provider layer metadata", () => {
+    expect(hasCompleteSeedreamLayerMetadata([
+      { z_index: 0, size: "2048x2048" },
+      { z_index: 1, size: "600x300" }
+    ], 2)).toBe(true);
+    expect(hasCompleteSeedreamLayerMetadata([
+      { size: "2048x2048" },
+      { size: "600x300" }
+    ], 2)).toBe(false);
+    expect(hasCompleteSeedreamLayerMetadata([{ z_index: 0 }], 2)).toBe(false);
+    expect(hasCompleteSeedreamLayerMetadata([{ z_index: 0 }], 1)).toBe(false);
+  });
+
   it("ships a versioned PostgreSQL document table that follows generation-job deletion", async () => {
     const migration = await readFile(new URL("../database/migrations/0005_seedream_layer_compositions.sql", import.meta.url), "utf8");