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/checker/command-runner.ts

@@ -0,0 +1,155 @@
+import type { CheckResult, ResolvedCommandTarget } from "./types";
+import { checkCommandExpect } from "./expect/command";
+import { errorFailure } from "./expect/failure";
+
+async function readOutput(
+  stdout: ReadableStream<Uint8Array>,
+  stderr: ReadableStream<Uint8Array>,
+  kill: () => void,
+  maxBytes: number,
+): Promise<{ stdout: string; stderr: string; exceeded: boolean }> {
+  let totalBytes = 0;
+  let exceeded = false;
+  let killed = false;
+
+  async function readStream(stream: ReadableStream<Uint8Array>): Promise<string> {
+    const reader = stream.getReader();
+    const decoder = new TextDecoder();
+    let text = "";
+
+    try {
+      while (true) {
+        const { done, value } = await reader.read();
+        if (done) break;
+        totalBytes += value.byteLength;
+        text += decoder.decode(value, { stream: true });
+        if (totalBytes > maxBytes && !killed) {
+          exceeded = true;
+          killed = true;
+          try {
+            kill();
+          } catch {
+            /* best-effort kill */
+          }
+        }
+      }
+    } catch {
+      /* stream already closed */
+    } finally {
+      try {
+        reader.releaseLock();
+      } catch {
+        /* already released */
+      }
+    }
+
+    return text;
+  }
+
+  const [out, err] = await Promise.all([readStream(stdout), readStream(stderr)]);
+
+  return { stdout: out, stderr: err, exceeded };
+}
+
+export async function runCommandCheck(target: ResolvedCommandTarget): Promise<CheckResult> {
+  const timestamp = new Date().toISOString();
+  const start = performance.now();
+
+  let proc: ReturnType<typeof Bun.spawn>;
+
+  try {
+    proc = Bun.spawn([target.command.exec, ...target.command.args], {
+      cwd: target.command.cwd,
+      env: target.command.env,
+      stdout: "pipe",
+      stderr: "pipe",
+    });
+  } catch (error) {
+    const durationMs = Math.round(performance.now() - start);
+    return {
+      targetName: target.name,
+      timestamp,
+      success: false,
+      matched: false,
+      durationMs,
+      statusDetail: null,
+      failure: errorFailure("exitCode", "spawn", error instanceof Error ? error.message : String(error)),
+    };
+  }
+
+  let timedOut = false;
+  const timeoutId = setTimeout(() => {
+    timedOut = true;
+    try {
+      proc.kill();
+    } catch {
+      /* best-effort kill */
+    }
+  }, target.timeoutMs);
+
+  let outputResult: { stdout: string; stderr: string; exceeded: boolean };
+
+  try {
+    outputResult = await readOutput(
+      proc.stdout as ReadableStream<Uint8Array>,
+      proc.stderr as ReadableStream<Uint8Array>,
+      () => proc.kill(),
+      target.command.maxOutputBytes,
+    );
+  } catch {
+    clearTimeout(timeoutId);
+    const durationMs = Math.round(performance.now() - start);
+    return {
+      targetName: target.name,
+      timestamp,
+      success: false,
+      matched: false,
+      durationMs,
+      statusDetail: null,
+      failure: errorFailure("exitCode", "execution", "输出读取失败"),
+    };
+  }
+
+  await proc.exited;
+  clearTimeout(timeoutId);
+
+  const durationMs = Math.round(performance.now() - start);
+  const exitCode = proc.exitCode ?? 1;
+
+  if (outputResult.exceeded) {
+    return {
+      targetName: target.name,
+      timestamp,
+      success: false,
+      matched: false,
+      durationMs,
+      statusDetail: `exitCode=${exitCode}`,
+      failure: errorFailure("exitCode", "output", `输出超过限制 ${target.command.maxOutputBytes} 字节`),
+    };
+  }
+
+  if (timedOut) {
+    return {
+      targetName: target.name,
+      timestamp,
+      success: false,
+      matched: false,
+      durationMs,
+      statusDetail: null,
+      failure: errorFailure("exitCode", "timeout", `命令执行超时 (${target.timeoutMs}ms)`),
+    };
+  }
+
+  const obs = { exitCode, stdout: outputResult.stdout, stderr: outputResult.stderr, durationMs };
+  const expectResult = checkCommandExpect(obs, target.expect);
+
+  return {
+    targetName: target.name,
+    timestamp,
+    success: expectResult.matched,
+    matched: expectResult.matched,
+    durationMs,
+    statusDetail: `exitCode=${exitCode}`,
+    failure: expectResult.failure,
+  };
+}