feat: 重构为多类型 checker 通用框架，支持 HTTP 与命令检查

- 引入 typed target 判别联合，支持 http 与 command 两种 checker
- expect 重构为有序规则数组，按配置顺序快速失败并生成结构化 failure
- 新增 command runner，支持 exec + args 本地命令执行
- 引入全局并发限制 maxConcurrentChecks 和 size 解析 (KB/MB/GB)
- HTTP/command 各自独立 expect pipeline，应用领域默认成功语义
- SQLite schema、API、Dashboard 全链路调整为 checker 通用契约
- 补充完整测试覆盖（192 tests），更新 README 与示例配置

src/server/app.ts

@@ -1,5 +1,6 @@
 import type {
   ApiErrorResponse,
+  CheckFailure,
   CheckResult,
   HealthResponse,
   RuntimeMode,
@@ -136,7 +137,7 @@ function handleTrend(idStr: string, url: URL, method: string, store: ProbeStore,
 
   const trend: TrendPoint[] = store.getTrend(id, hours).map((row) => ({
     hour: row.hour,
-    avgLatencyMs: row.avgLatencyMs,
+    avgDurationMs: row.avgDurationMs,
     availability: Math.round(row.availability * 100) / 100,
     totalChecks: row.totalChecks,
   }));
@@ -150,7 +151,7 @@ function createSummaryResponse(store: ProbeStore): SummaryResponse {
     total: summary.total,
     up: summary.up,
     down: summary.down,
-    avgLatencyMs: summary.avgLatencyMs,
+    avgDurationMs: summary.avgDurationMs,
     lastCheckTime: summary.lastCheckTime,
   };
 }
@@ -165,29 +166,34 @@ function createTargetsResponse(store: ProbeStore): TargetStatus[] {
     return {
       id: target.id,
       name: target.name,
-      url: target.url,
-      method: target.method,
+      type: target.type,
+      target: target.target,
       interval: formatDuration(target.interval_ms),
       latestCheck: latest ? mapCheckResult(latest) : null,
       sparkline: store.getSparkline(target.id),
       stats: {
         totalChecks: stats.totalChecks,
         availability: stats.availability,
-        avgLatencyMs: stats.avgLatencyMs,
-        p99LatencyMs: stats.p99LatencyMs,
+        avgDurationMs: stats.avgDurationMs,
+        p99DurationMs: stats.p99DurationMs,
       },
     };
   });
 }
 
 function mapCheckResult(row: StoredCheckResult): CheckResult {
+  let failure: CheckFailure | null = null;
+  if (row.failure) {
+    failure = JSON.parse(row.failure) as CheckFailure;
+  }
+
   return {
     timestamp: row.timestamp,
     success: row.success === 1,
-    statusCode: row.status_code,
-    latencyMs: row.latency_ms,
-    error: row.error,
     matched: row.matched === 1,
+    durationMs: row.duration_ms,
+    statusDetail: row.status_detail,
+    failure,
   };
 }