refactor: 重命名 command checker 为 cmd checker 并适配跨平台测试

将 type/configKey 从 "command" 统一为 "cmd"，源码目录 runner/command/ → runner/cmd/，
spec 目录 command-checker/ → cmd-checker/，测试全部改用 bun -e 替代 Unix 系统命令，
归档 cmd-checker-enhancement 变更并同步 delta spec 到主 spec。

tests/server/checker/runner/cmd/expect.test.ts

@@ -0,0 +1,26 @@
+import { describe, expect, test } from "bun:test";
+
+import { checkExitCode } from "../../../../../src/server/checker/runner/cmd/expect";
+
+describe("checkExitCode", () => {
+  test("exitCode 在允许列表中匹配成功", () => {
+    const r = checkExitCode(0, [0]);
+    expect(r.matched).toBe(true);
+    expect(r.failure).toBeNull();
+  });
+
+  test("exitCode 不在允许列表中匹配失败", () => {
+    const r = checkExitCode(1, [0]);
+    expect(r.matched).toBe(false);
+    expect(r.failure!.phase).toBe("exitCode");
+    expect(r.failure!.kind).toBe("mismatch");
+    expect(r.failure!.expected).toEqual([0]);
+    expect(r.failure!.actual).toBe(1);
+  });
+
+  test("多个允许退出码", () => {
+    expect(checkExitCode(0, [0, 1]).matched).toBe(true);
+    expect(checkExitCode(1, [0, 1]).matched).toBe(true);
+    expect(checkExitCode(2, [0, 1]).matched).toBe(false);
+  });
+});