refactor: 引入 Checker 统一接口与 Runner 抽象机制

定义 Checker 接口（resolve/execute/serialize）和 CheckerRegistry
注册中心，消除 engine/config-loader/store 中硬编码类型分支。
按 checker 类型分子包（runner/http/、runner/command/），提取
共享 expect 到 runner/shared/。超时控制通过引擎注入 AbortSignal。
CheckFailure.phase 从联合类型改为 string。配置校验下沉到各
Checker.resolve() 内部。

新增 checker-runner-abstraction spec，更新 DEVELOPMENT.md。

tests/server/checker/runner/command/runner.test.ts

@@ -0,0 +1,116 @@
+import { describe, expect, test } from "bun:test";
+import { CommandChecker } from "../../../../../src/server/checker/runner/command/runner";
+import type { CheckerContext } from "../../../../../src/server/checker/runner/types";
+import type { ResolvedCommandTarget } from "../../../../../src/server/checker/types";
+
+const checker = new CommandChecker();
+
+function makeTarget(
+  command: Partial<ResolvedCommandTarget["command"]>,
+  overrides?: Partial<ResolvedCommandTarget>,
+): ResolvedCommandTarget {
+  return {
+    type: "command",
+    name: "test-cmd",
+    group: "default",
+    command: {
+      exec: "echo",
+      args: ["hello"],
+      cwd: "/tmp",
+      env: {},
+      maxOutputBytes: 1024 * 1024,
+      ...command,
+    },
+    intervalMs: 60000,
+    timeoutMs: 5000,
+    ...overrides,
+  };
+}
+
+function makeCtx(timeoutMs = 5000): CheckerContext {
+  const controller = new AbortController();
+  setTimeout(() => controller.abort(), timeoutMs);
+  return { signal: controller.signal };
+}
+
+describe("CommandChecker", () => {
+  test("exitCode=0 成功", async () => {
+    const result = await checker.execute(makeTarget({ exec: "true", args: [] }), makeCtx());
+    expect(result.matched).toBe(true);
+    expect(result.statusDetail).toBe("exitCode=0");
+    expect(result.failure).toBeNull();
+  });
+
+  test("exitCode=1 不匹配默认 [0]", async () => {
+    const result = await checker.execute(makeTarget({ exec: "false", args: [] }), makeCtx());
+    expect(result.matched).toBe(false);
+    expect(result.statusDetail).toBe("exitCode=1");
+    expect(result.failure!.phase).toBe("exitCode");
+  });
+
+  test("exitCode=1 匹配自定义 [1]", async () => {
+    const result = await checker.execute(makeTarget({ exec: "false", args: [] }, { expect: { exitCode: [1] } }), makeCtx());
+    expect(result.matched).toBe(true);
+    expect(result.statusDetail).toBe("exitCode=1");
+  });
+
+  test("命令不存在返回 spawn 错误", async () => {
+    const result = await checker.execute(makeTarget({ exec: "/nonexistent/command/xyz" }), makeCtx());
+    expect(result.matched).toBe(false);
+    expect(result.failure!.phase).toBe("exitCode");
+    expect(result.failure!.message).toBeTruthy();
+  });
+
+  test("超时返回错误", async () => {
+    const result = await checker.execute(makeTarget({ exec: "sleep", args: ["10"] }, { timeoutMs: 100 }), makeCtx(100));
+    expect(result.matched).toBe(false);
+    expect(result.failure!.message).toContain("超时");
+  });
+
+  test("stdout 输出捕获", async () => {
+    const result = await checker.execute(makeTarget({ exec: "echo", args: ["hello world"] }), makeCtx());
+    expect(result.matched).toBe(true);
+  });
+
+  test("stdout 匹配 expect", async () => {
+    const result = await checker.execute(makeTarget({ exec: "echo", args: ["hello"] }, { expect: { stdout: [{ contains: "hello" }] } }), makeCtx());
+    expect(result.matched).toBe(true);
+  });
+
+  test("stdout 不匹配 expect", async () => {
+    const result = await checker.execute(makeTarget({ exec: "echo", args: ["hello"] }, { expect: { stdout: [{ contains: "nonexistent" }] } }), makeCtx());
+    expect(result.matched).toBe(false);
+    expect(result.failure!.phase).toBe("stdout");
+  });
+
+  test("stderr 匹配 expect", async () => {
+    const result = await checker.execute(makeTarget({ exec: "bash", args: ["-c", "echo error >&2"] }, { expect: { stderr: [{ contains: "error" }] } }), makeCtx());
+    expect(result.matched).toBe(true);
+  });
+
+  test("输出超过 maxOutputBytes", async () => {
+    const result = await checker.execute(makeTarget({ exec: "bash", args: ["-c", "yes | head -1000"], maxOutputBytes: 10 }), makeCtx());
+    expect(result.matched).toBe(false);
+    expect(result.failure!.message).toContain("超过限制");
+  });
+
+  test("durationMs 非空", async () => {
+    const result = await checker.execute(makeTarget({ exec: "true", args: [] }), makeCtx());
+    expect(result.durationMs).not.toBeNull();
+    expect(result.durationMs!).toBeGreaterThanOrEqual(0);
+  });
+
+  test("不使用 shell，通配符不被展开", async () => {
+    const result = await checker.execute(makeTarget({ exec: "echo", args: ["*"] }, { expect: { stdout: [{ contains: "*" }] } }), makeCtx());
+    expect(result.matched).toBe(true);
+  });
+
+  test("serialize 返回命令摘要和 config JSON", () => {
+    const target = makeTarget({ exec: "echo", args: ["hello"] });
+    const s = checker.serialize(target);
+    expect(s.target).toBe("exec echo hello");
+    const config = JSON.parse(s.config);
+    expect(config.exec).toBe("echo");
+    expect(config.args).toEqual(["hello"]);
+  });
+});