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/config-loader.test.ts

@@ -5,6 +5,7 @@ import { join } from "node:path";
 
 import type { ResolvedCommandTarget } from "../../../src/server/checker/runner/cmd/types";
 import type { ResolvedHttpTarget } from "../../../src/server/checker/runner/http/types";
+import type { ResolvedPingTarget } from "../../../src/server/checker/runner/icmp/types";
 import type { ResolvedTcpTarget } from "../../../src/server/checker/runner/tcp/types";
 
 import { loadConfig, parseDuration } from "../../../src/server/checker/config-loader";
@@ -1974,4 +1975,99 @@ targets:
     expect(t.expect?.connected).toBe(false);
     expect(t.expect?.maxDurationMs).toBe(5000);
   });
+
+  test("解析最简 ping 配置", async () => {
+    const configPath = join(tempDir, "minimal-ping.yaml");
+    await writeFile(
+      configPath,
+      `targets:
+  - id: "gateway"
+    type: ping
+    ping:
+      host: "10.0.0.1"
+`,
+    );
+
+    const config = await loadConfig(configPath);
+    expect(config.targets).toHaveLength(1);
+    const t = config.targets[0]! as ResolvedPingTarget;
+    expect(t.type).toBe("ping");
+    expect(t.ping).toEqual({ count: 3, host: "10.0.0.1", packetSize: 56 });
+    expect(t.group).toBe("default");
+    expect(t.intervalMs).toBe(30000);
+    expect(t.timeoutMs).toBe(10000);
+  });
+
+  test("解析 ping expect 配置", async () => {
+    const configPath = join(tempDir, "ping-expect.yaml");
+    await writeFile(
+      configPath,
+      `targets:
+  - id: "gateway"
+    type: ping
+    ping:
+      host: "10.0.0.1"
+      count: 5
+      packetSize: 1472
+    expect:
+      alive: true
+      maxPacketLoss: 10
+      maxAvgLatencyMs: 200
+      maxMaxLatencyMs: 500
+      maxDurationMs: 5000
+`,
+    );
+
+    const config = await loadConfig(configPath);
+    const t = config.targets[0]! as ResolvedPingTarget;
+    expect(t.ping).toEqual({ count: 5, host: "10.0.0.1", packetSize: 1472 });
+    expect(t.expect).toEqual({
+      alive: true,
+      maxAvgLatencyMs: 200,
+      maxDurationMs: 5000,
+      maxMaxLatencyMs: 500,
+      maxPacketLoss: 10,
+    });
+  });
+
+  test("ping 缺少 host 抛出错误", async () => {
+    await expectConfigError(
+      "ping-no-host.yaml",
+      `targets:
+  - id: "gateway"
+    type: ping
+    ping: {}
+`,
+      "ping.host",
+    );
+  });
+
+  test("ping count 非法抛出错误", async () => {
+    await expectConfigError(
+      "ping-bad-count.yaml",
+      `targets:
+  - id: "gateway"
+    type: ping
+    ping:
+      host: "10.0.0.1"
+      count: 0
+`,
+      "ping.count",
+    );
+  });
+
+  test("ping expect 未知字段抛出错误", async () => {
+    await expectConfigError(
+      "ping-unknown-expect.yaml",
+      `targets:
+  - id: "gateway"
+    type: ping
+    ping:
+      host: "10.0.0.1"
+    expect:
+      status: [200]
+`,
+      "expect.status 是未知字段",
+    );
+  });
 });