feat: add 23 GMP questions to go-java-concurrency

新增题目覆盖 Go GMP 调度模型核心知识点：
- 单选 ×10: G状态机、M角色、GOMAXPROCS、netpoller、信号抢占、
  runtime.schedule、work-stealing、连续栈、sysmon、channel调度
- 判断 ×5: G状态转换、SIGURG异步抢占、本地队列容量、hand-off、栈保护
- 填空 ×5: GOMAXPROCS默认值、调度顺序、stackguard0、SIGURG、GOMAXPROCS(0)
- 代码阅读 ×3: 调度交错、M/P hand-off、无缓冲channel同步

Total: 45 → 68 questions

topics/index.json

@@ -1,6 +1,6 @@
 {
   "version": "1.0.0",
-  "updated": "2026-09-09",
+  "updated": "2026-09-13",
   "topics": [
     {
       "slug": "qunar-ai-fullstack",
@@ -399,13 +399,13 @@
           "description": "GMP调度、CSP模型、AQS/ForkJoinPool、goroutine泄漏、JMM、happens-before、pprof/JFR",
           "path": "topics/interview-prep/go-java-concurrency",
           "stats": {
-            "total": 45,
+            "total": 68,
             "by_type": {
-              "single_choice": 15,
-              "true_false": 10,
-              "fill_blank": 10,
+              "single_choice": 25,
+              "true_false": 15,
+              "fill_blank": 15,
               "short_answer": 5,
-              "code_reading": 5
+              "code_reading": 8
             }
           }
         },
@@ -521,4 +521,4 @@
       ]
     }
   ]
-}
+}