refactor: ICMP checker type 从 ping 统一改为 icmp，修复前端 UI 细节

- ICMP checker 的 type/configKey/YAML 配置键/接口属性名从 ping 改为 icmp
- IcmpChecker 添加 platform 构造函数注入，修复 Windows 测试兼容性
- 前端 target 表格延迟列优化：标题简化为「延迟」，单位下移到单元格，宽度 80px
- Drawer 概览页 Descriptions 添加 tableLayout=auto 收窄 label 宽度
- 同步更新 README.md、DEVELOPMENT.md、probes.example.yaml、JSON Schema 和全部测试

tests/server/checker/config-loader.test.ts

@@ -2009,14 +2009,14 @@ targets:
     expect(t.expect?.durationMs).toEqual({ lte: 5000 });
   });
 
-  test("解析最简 ping 配置", async () => {
-    const configPath = join(tempDir, "minimal-ping.yaml");
+  test("解析最简 icmp 配置", async () => {
+    const configPath = join(tempDir, "minimal-icmp.yaml");
     await writeFile(
       configPath,
       `targets:
   - id: "gateway"
-    type: ping
-    ping:
+    type: icmp
+    icmp:
       host: "10.0.0.1"
 `,
     );
@@ -2024,21 +2024,21 @@ targets:
     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.type).toBe("icmp");
+    expect(t.icmp).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");
+  test("解析 icmp expect 配置", async () => {
+    const configPath = join(tempDir, "icmp-expect.yaml");
     await writeFile(
       configPath,
       `targets:
   - id: "gateway"
-    type: ping
-    ping:
+    type: icmp
+    icmp:
       host: "10.0.0.1"
       count: 5
       packetSize: 1472
@@ -2057,7 +2057,7 @@ targets:
 
     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.icmp).toEqual({ count: 5, host: "10.0.0.1", packetSize: 1472 });
     expect(t.expect).toEqual({
       alive: true,
       avgLatencyMs: { lte: 200 },
@@ -2067,39 +2067,39 @@ targets:
     });
   });
 
-  test("ping 缺少 host 抛出错误", async () => {
+  test("icmp 缺少 host 抛出错误", async () => {
     await expectConfigError(
-      "ping-no-host.yaml",
+      "icmp-no-host.yaml",
       `targets:
   - id: "gateway"
-    type: ping
-    ping: {}
+    type: icmp
+    icmp: {}
 `,
-      "ping.host",
+      "icmp.host",
     );
   });
 
-  test("ping count 非法抛出错误", async () => {
+  test("icmp count 非法抛出错误", async () => {
     await expectConfigError(
-      "ping-bad-count.yaml",
+      "icmp-bad-count.yaml",
       `targets:
   - id: "gateway"
-    type: ping
-    ping:
+    type: icmp
+    icmp:
       host: "10.0.0.1"
       count: 0
 `,
-      "ping.count",
+      "icmp.count",
     );
   });
 
-  test("ping expect 未知字段抛出错误", async () => {
+  test("icmp expect 未知字段抛出错误", async () => {
     await expectConfigError(
-      "ping-unknown-expect.yaml",
+      "icmp-unknown-expect.yaml",
       `targets:
   - id: "gateway"
-    type: ping
-    ping:
+    type: icmp
+    icmp:
       host: "10.0.0.1"
     expect:
       status: [200]