修复了一点bug，然后增加了图层拆分更多的功能

tests/seedream-layer-compositions.test.ts

@@ -0,0 +1,28 @@
+import { readFile } from "node:fs/promises";
+import { describe, expect, it } from "vitest";
+
+describe("Seedream layer composition persistence contract", () => {
+  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");
+
+    expect(migration).toContain("create table if not exists public.seedream_layer_compositions");
+    expect(migration).toContain("references public.generation_jobs(id) on delete cascade");
+    expect(migration).toContain("layers jsonb not null");
+    expect(migration).toContain("version bigint not null");
+    expect(migration).toContain("jsonb_typeof(layers) = 'array'");
+  });
+
+  it("exposes owner-scoped GET/PUT routes and provisions application-role privileges", async () => {
+    const [surface, privileges, handler] = await Promise.all([
+      readFile(new URL("../contracts/http/route-surface.v1.json", import.meta.url), "utf8"),
+      readFile(new URL("../scripts/migrate-postgres.mjs", import.meta.url), "utf8"),
+      readFile(new URL("../backend/internal/httpapi/layer_compositions.go", import.meta.url), "utf8")
+    ]);
+
+    expect(surface).toContain('"GET", "path": "/api/layer-compositions/{id}"');
+    expect(surface).toContain('"PUT", "path": "/api/layer-compositions/{id}"');
+    expect(privileges).toContain('["seedream_layer_compositions", "SELECT, INSERT, UPDATE, DELETE"]');
+    expect(handler).toContain("handler.platform.Authorize");
+    expect(handler).toContain("jobs.Scope{OwnerID: session.User.ID}");
+  });
+});