清理 #180 终审遗留：删 notes_processor 不可达守卫，修正测试表述，补纯空白输入用例 (#185) - #189

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@11d5960a326750d5838078e36cf38b85af677262. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/