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/icmp/execute.test.ts

@@ -60,7 +60,10 @@ rtt min/avg/max/mdev = 1.234/2.345/3.456/0.567 ms`);
 
   test("alive 失败短路", async () => {
     mockSpawn(`3 packets transmitted, 0 received, 100% packet loss, time 2003ms`);
-    const result = await checker.execute(makeTarget({ expect: { alive: true, maxAvgLatencyMs: 100 } }), makeCtx());
+    const result = await checker.execute(
+      makeTarget({ expect: { alive: true, avgLatencyMs: { lte: 100 } } }),
+      makeCtx(),
+    );
     expect(result.matched).toBe(false);
     expect(result.failure?.phase).toBe("alive");
     expect(result.statusDetail).toBe("unreachable (0/3 received)");
@@ -75,7 +78,7 @@ rtt min/avg/max/mdev = 1.234/2.345/3.456/0.567 ms`);
   test("packetLoss 断言失败", async () => {
     mockSpawn(`3 packets transmitted, 2 received, 33% packet loss, time 2003ms
 rtt min/avg/max/mdev = 1.234/156.000/340.000/0.567 ms`);
-    const result = await checker.execute(makeTarget({ expect: { maxPacketLoss: 10 } }), makeCtx());
+    const result = await checker.execute(makeTarget({ expect: { packetLossPercent: { lte: 10 } } }), makeCtx());
     expect(result.matched).toBe(false);
     expect(result.failure?.phase).toBe("packetLoss");
     expect(result.statusDetail).toContain("max 340ms");