feat: 新增 memory checker，支持系统级内存和交换空间检测

tests/server/checker/runner/registry.test.ts

@@ -84,9 +84,22 @@ describe("CheckerRegistry", () => {
       "dns",
       "ws",
       "cpu",
+      "memory",
       "custom",
     ]);
-    expect(second.supportedTypes).toEqual(["http", "cmd", "db", "tcp", "icmp", "udp", "llm", "dns", "ws", "cpu"]);
+    expect(second.supportedTypes).toEqual([
+      "http",
+      "cmd",
+      "db",
+      "tcp",
+      "icmp",
+      "udp",
+      "llm",
+      "dns",
+      "ws",
+      "cpu",
+      "memory",
+    ]);
     expect(
       first.definitions.every((checker) => checker.schemas.authoring.config && checker.schemas.normalized.expect),
     ).toBe(true);