refactor: 修复代码审查发现的问题

- Bug修复: formatChangeStatus 使用实际配置而非 defaultConfig
- 统一 assembler 中所有错误抛出为 CommandError
- 提取 writeIfChanged 到 adapters/utils.ts，消除 claude-code/opencode 重复代码
- 导出 SUPPORTED_TOOLS，cli.ts update 命令复用同一工具注册表
- 提取 mapError/mapCacError 函数，支持单元测试
- 补充 claude-code 适配器测试（10 个用例）
- 补充 validateChangeName、formatChangeStatus、suggestNextStep、mapError 单元测试（18 个用例）
- 共新增 3 个测试文件，测试从 96 增至 133，全部通过

tests/cli/map-error.test.ts

@@ -0,0 +1,62 @@
+import { describe, it, expect } from "bun:test";
+import {
+  CliError,
+  UsageError,
+  ConfigError,
+  CommandError,
+  InternalError,
+} from "../../src/cli/errors.ts";
+import { mapError } from "../../src/cli.ts";
+
+describe("mapError", () => {
+  it("CliError 原样返回", () => {
+    const err = new ConfigError("未初始化");
+    const result = mapError(err);
+    expect(result).toBe(err);
+    expect(result.message).toBe("未初始化");
+  });
+
+  it("Unknown option 转为 UsageError", () => {
+    const err = new Error("Unknown option `--badflag`");
+    const result = mapError(err);
+    expect(result).toBeInstanceOf(UsageError);
+    expect(result.message).toBe("未知选项: --badflag");
+    expect(result.hint).toBe("运行 rune help 查看所有命令");
+  });
+
+  it("Unknown command 转为 UsageError", () => {
+    const err = new Error("Unknown command `foo`");
+    const result = mapError(err);
+    expect(result).toBeInstanceOf(UsageError);
+    expect(result.message).toBe("未知命令: foo");
+  });
+
+  it("Unused args 转为 UsageError", () => {
+    const err = new Error("Unused args: --extra");
+    const result = mapError(err);
+    expect(result).toBeInstanceOf(UsageError);
+    expect(result.message).toContain("未知命令");
+    expect(result.message).toContain("--extra");
+  });
+
+  it("missing required args 转为 UsageError", () => {
+    const err = new Error("missing required args for command `plan`");
+    const result = mapError(err);
+    expect(result).toBeInstanceOf(UsageError);
+    expect(result.message).toBe("命令 'plan' 缺少必填参数");
+    expect(result.usage).toBe("rune plan <change-name>");
+    expect(result.hint).toContain("rune help plan");
+  });
+
+  it("未知 Error 转为 InternalError", () => {
+    const err = new Error("something unexpected");
+    const result = mapError(err);
+    expect(result).toBeInstanceOf(InternalError);
+    expect(result.message).toBe("发生了未预期的错误");
+  });
+
+  it("非 Error 类型转为 InternalError", () => {
+    const result = mapError("字符串错误");
+    expect(result).toBeInstanceOf(InternalError);
+  });
+});