feat: 新增 ICMP/Ping checker，支持跨平台主机存活检测与延迟监控

实现 type: ping checker，通过 Bun.spawn 调用系统 ping 命令，自行实现跨平台
输出解析器（Linux/macOS/Windows 含中文 locale），支持 alive、丢包率、延迟、
耗时等 expect 断言，复用现有 checker 架构零外部依赖。

包含完整的类型定义、TypeBox schema、语义校验、命令构建、解析、断言、执行、
注册、配置加载测试，以及 probe-config.schema.json 更新和文档更新。

审查修复：提取 buildPingCommand 为独立纯函数并补充跨平台单测，补充
maxDurationMs/maxAvgLatencyMs 类型非法和空字符串 host 边界测试用例。

变更已归档，delta specs 已同步至 main specs。

tests/server/checker/runner/icmp/execute.test.ts

@@ -0,0 +1,126 @@
+import { afterEach, describe, expect, mock, test } from "bun:test";
+
+import type { ResolvedPingTarget } from "../../../../../src/server/checker/runner/icmp/types";
+import type { CheckerContext } from "../../../../../src/server/checker/runner/types";
+
+import { IcmpChecker } from "../../../../../src/server/checker/runner/icmp/execute";
+
+const checker = new IcmpChecker();
+const originalSpawn = Bun.spawn;
+
+afterEach(() => {
+  Bun.spawn = originalSpawn;
+  mock.restore();
+});
+
+function makeCtx(): CheckerContext {
+  return { signal: new AbortController().signal };
+}
+
+function makeTarget(overrides?: Partial<ResolvedPingTarget>): ResolvedPingTarget {
+  return {
+    description: null,
+    group: "default",
+    id: "ping-local",
+    intervalMs: 30000,
+    name: null,
+    ping: { count: 3, host: "127.0.0.1", packetSize: 56 },
+    timeoutMs: 10000,
+    type: "ping",
+    ...overrides,
+  };
+}
+
+function mockSpawn(stdout: string, exitCode = 0) {
+  const calls: string[][] = [];
+  const spawnMock = mock((command: string[]) => {
+    calls.push(command);
+    return {
+      exitCode,
+      exited: Promise.resolve(exitCode),
+      kill: mock(() => undefined),
+      stderr: new Response("").body,
+      stdout: new Response(stdout).body,
+    };
+  });
+  Bun.spawn = spawnMock as unknown as typeof Bun.spawn;
+  return calls;
+}
+
+describe("IcmpChecker execute", () => {
+  test("执行 ping 并匹配默认 alive", async () => {
+    const calls = mockSpawn(`3 packets transmitted, 3 received, 0% packet loss, time 2003ms
+rtt min/avg/max/mdev = 1.234/2.345/3.456/0.567 ms`);
+    const result = await checker.execute(makeTarget(), makeCtx());
+    expect(result.matched).toBe(true);
+    expect(result.failure).toBeNull();
+    expect(result.statusDetail).toBe("alive, avg 2.345ms, loss 0% (3/3)");
+    expect(calls[0]).toContain("ping");
+  });
+
+  test("alive 失败短路", async () => {
+    mockSpawn(`3 packets transmitted, 0 received, 100% packet loss, time 2003ms`);
+    const result = await checker.execute(makeTarget({ expect: { alive: true, maxAvgLatencyMs: 100 } }), makeCtx());
+    expect(result.matched).toBe(false);
+    expect(result.failure?.phase).toBe("alive");
+    expect(result.statusDetail).toBe("unreachable (0/3 received)");
+  });
+
+  test("反向 alive 断言通过", async () => {
+    mockSpawn(`3 packets transmitted, 0 received, 100% packet loss, time 2003ms`);
+    const result = await checker.execute(makeTarget({ expect: { alive: false } }), makeCtx());
+    expect(result.matched).toBe(true);
+  });
+
+  test("packetLoss 断言失败", async () => {
+    mockSpawn(`3 packets transmitted, 2 received, 33% packet loss, time 2003ms
+rtt min/avg/max/mdev = 1.234/156.000/340.000/0.567 ms`);
+    const result = await checker.execute(makeTarget({ expect: { maxPacketLoss: 10 } }), makeCtx());
+    expect(result.matched).toBe(false);
+    expect(result.failure?.phase).toBe("packetLoss");
+    expect(result.statusDetail).toContain("max 340ms");
+  });
+
+  test("解析失败返回结构化错误", async () => {
+    mockSpawn("unexpected output");
+    const result = await checker.execute(makeTarget(), makeCtx());
+    expect(result.matched).toBe(false);
+    expect(result.failure).toMatchObject({ kind: "error", path: "parse", phase: "ping" });
+  });
+
+  test("spawn 失败返回 ping 命令不可用", async () => {
+    Bun.spawn = mock(() => {
+      throw new Error("ENOENT");
+    });
+    const result = await checker.execute(makeTarget(), makeCtx());
+    expect(result.matched).toBe(false);
+    expect(result.failure?.message).toContain("ping 命令不可用");
+    expect(result.statusDetail).toBe("ping command not found");
+  });
+
+  test("预 abort 返回超时错误", async () => {
+    mockSpawn(`3 packets transmitted, 3 received, 0% packet loss, time 2003ms`);
+    const controller = new AbortController();
+    controller.abort();
+    const result = await checker.execute(makeTarget(), { signal: controller.signal });
+    expect(result.matched).toBe(false);
+    expect(result.failure).toMatchObject({ path: "timeout", phase: "ping" });
+  });
+});
+
+describe("IcmpChecker resolve", () => {
+  test("解析默认值", () => {
+    const target = checker.resolve(
+      { id: "ping", ping: { host: "10.0.0.1" }, type: "ping" },
+      { configDir: "/tmp", defaultIntervalMs: 30000, defaults: {}, defaultTimeoutMs: 10000 },
+    );
+    expect(target.ping).toEqual({ count: 3, host: "10.0.0.1", packetSize: 56 });
+    expect(target.group).toBe("default");
+  });
+
+  test("serialize 返回摘要和配置", () => {
+    const serialized = checker.serialize(makeTarget({ ping: { count: 5, host: "10.0.0.1", packetSize: 1472 } }));
+    expect(serialized.target).toBe("ping 10.0.0.1");
+    expect(JSON.parse(serialized.config)).toEqual({ count: 5, host: "10.0.0.1", packetSize: 1472 });
+  });
+});