refactor: 统一 expect 断言体系，引入共享 ValueMatcher/ContentRules/KeyValueExpect 模型

- 引入共享 ValueMatcher（equals/contains/regex/exists/empty/gt/gte/lt/lte）
- 引入共享 ContentRules 数组（direct/json/css/xpath 提取器）
- 引入共享 KeyValueExpect（动态键值断言，字面量等价 equals）
- maxDurationMs → durationMs: ValueMatcher（所有 checker）
- match → regex（固定无 flags）
- Ping max* → packetLossPercent/avgLatencyMs/maxLatencyMs（ValueMatcher）
- LLM finishReason/rawFinishReason → ValueMatcher
- DB 新增 result: ContentRules
- TCP banner → ContentRules 数组
- 删除旧模块：operator.ts、validate-operator.ts、duration.ts、body.ts、text.ts、output.ts
- 更新全部 checker schema/validate/expect/execute
- 更新 probe-config.schema.json、probes.example.yaml
- 更新 README.md、DEVELOPMENT.md（含 expect 字段选择规范）
- 同步 10 个 delta specs 到主 specs，归档 change

tests/server/checker/runner/udp/execute.test.ts

@@ -250,7 +250,7 @@ describe("UdpChecker execute", () => {
     }
   });
 
-  it("should fail when duration exceeds maxDurationMs", async () => {
+  it("should fail when duration exceeds durationMs", async () => {
     const server = await Bun.udpSocket({
       socket: {
         data() {
@@ -266,7 +266,7 @@ describe("UdpChecker execute", () => {
     });
     try {
       const checker = new UdpChecker();
-      const target = makeTarget({ port: server.port }, { maxDurationMs: 1, responded: false });
+      const target = makeTarget({ port: server.port }, { durationMs: { lte: 1 }, responded: false });
       const controller = new AbortController();
       const timer = setTimeout(() => controller.abort(), 200);
       const result = await checker.execute(target, { signal: controller.signal });