feat(skill): beta 技能 diagnosing-bugs + 月度审阅与 evals 工具

- 新增 diagnosing-bugs（beta）：先建红循环再推理、二分定位、补回归测试；含 evals 与四段式文档
- 路由表加入难查 bug 行
- scripts/monthly-review.sh：一条命令跑月度审阅
- scripts/evals-status.py + reports/evals/TEMPLATE.md：evals 覆盖与回归报告模板
- skill-creator 实战记录 #1（待观察后晋升）

skills-dev/diagnosing-bugs-plugin/.claude-plugin/plugin.json

@@ -0,0 +1,11 @@
+{
+  "name": "diagnosing-bugs-plugin",
+  "description": "难查 bug 的诊断纪律：先造出会变红的紧反馈循环，再二分定位、最小验证、补回归测试。",
+  "version": "0.1.0",
+  "author": { "name": "qiudl" },
+  "install_name": "diagnosing-bugs",
+  "install_type": "skill",
+  "dir_category": "dev",
+  "status": "beta",
+  "invocation": "model-invoked"
+}