refactor: create 从 SDD 阶段降级为工具命令，移除阶段配置和提示词

tests/core/assembler.test.ts

@@ -3,14 +3,12 @@ import { mkdir, writeFile, rm } from "node:fs/promises";
 import { join } from "node:path";
 import {
   assembleDiscussPrompt,
-  assembleCreatePrompt,
   assemblePlanPrompt,
   assembleBuildPrompt,
   assembleArchivePrompt,
 } from "../../src/core/assembler.ts";
 import type { RuneConfig } from "../../src/types.ts";
 import { defaultConfig } from "../../src/defaults/config.ts";
-import { CommandError } from "../../src/cli/errors.ts";
 
 const TMP_DIR = join(import.meta.dir, "__tmp_assembler_test__");
 
@@ -40,35 +38,6 @@ describe("assembleDiscussPrompt", () => {
   });
 });
 
-describe("assembleCreatePrompt", () => {
-  it("返回默认 create 提示词", () => {
-    const prompt = assembleCreatePrompt(defaultConfig);
-    expect(prompt).toBeTruthy();
-    expect(prompt).toContain("变更名称");
-    expect(prompt).toContain("/rune-plan");
-  });
-
-  it("返回自定义 create 提示词", () => {
-    const config: RuneConfig = {
-      stages: { create: { prompt: "自定义创建" } },
-    };
-    const prompt = assembleCreatePrompt(config);
-    expect(prompt).toBe("自定义创建");
-  });
-
-  it("create 阶段未配置时抛出 CommandError", () => {
-    const config: RuneConfig = {
-      stages: { build: { prompt: "构建" } },
-    };
-    try {
-      assembleCreatePrompt(config);
-      expect.unreachable();
-    } catch (e) {
-      expect(e).toBeInstanceOf(CommandError);
-    }
-  });
-});
-
 describe("assemblePlanPrompt", () => {
   it("包含指定文档名称和提示词", async () => {
     const prompt = await assemblePlanPrompt(defaultConfig, TMP_DIR, "user-auth", "design");