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

scripts/clean.ts

@@ -1,4 +1,4 @@
-import { readdir, rm } from "node:fs/promises";
+import { rm } from "node:fs/promises";
 import { resolve } from "node:path";
 
 const root = resolve(import.meta.dir, "..");
@@ -9,7 +9,7 @@ const patterns: Array<{ glob: string; desc: string }> = [
 ];
 
 for (const { glob, desc } of patterns) {
-  const entries = await Array.fromAsync(new Bun.Glob(glob).scan({ root, dot: true }));
+  const entries = await Array.fromAsync(new Bun.Glob(glob).scan({ cwd: root, dot: true }));
   if (entries.length === 0) continue;
   for (const entry of entries) {
     const full = resolve(root, entry);

scripts/smoke.ts

@@ -16,7 +16,9 @@ writeFileSync(
   configPath,
   `targets:
   - name: "httpbin"
-    url: "https://httpbin.org/get"
+    type: http
+    http:
+      url: "https://httpbin.org/get"
     interval: "5m"
     timeout: "15s"
     expect: