refactor: 移除模板变量 {{change-name}} 替换功能，模板改为纯静态文本

tests/defaults/config.test.ts

@@ -66,7 +66,7 @@ describe("defaultConfig", () => {
   it("design 文档有 template", () => {
     const designDoc = defaultConfig.stages.plan!.documents.find((d) => d.name === "design");
     expect(designDoc!.template).toBeTruthy();
-    expect(designDoc!.template).toContain("{{change-name}}");
+    expect(designDoc!.template).toContain("设计文档");
   });
 
   it("task 文档有 template", () => {