docs: record recurring defect types and the mechanism covering each

The titlebar drag-region defect was fixed three times in a row, each time
only for the dialogs someone reported, and the same batch introduced two more
instances. Repeated full-table lookups and production reuse of a verification
helper showed up in several places at once for the same reason.

Add docs/quality/recurring-defects.md describing each type that has actually
recurred here, the shared mechanism or automated test that now covers it, and
the history that justifies the entry. Require reading it from AGENTS.md before
touching overlays, store lookups, retrieval entry points, cancellation, or
render-time derived values, and require extending the shared mechanism rather
than patching one reported case.

Correct the external knowledge technical design where it described the removed
configuration-snapshot checks, the shared retrieval entry point and the
unreachable probe status, and record the refactor and its validation in the
knowledge base progress log.

docs/quality/README.md

@@ -5,6 +5,7 @@
 | 文档 | 职责 |
 | --- | --- |
 | [Electron UI 自动化测试规范](./electron-ui-automation.md) | 测试分层、当前源码启动、视觉与原生交互取证、真实调用计数、脱敏报告和清理 |
+| [复发缺陷与防复发规则](./recurring-defects.md) | 已重复出现的缺陷类型、对应的共享机制和自动发现测试 |
 | [开发与构建](../../BUILD.md#质量验证) | 依赖、测试、类型检查、Lint 和构建命令 |
 | [UI 设计系统](../../UI-DESIGN.md#155-验收) | 全局视觉、交互和响应式验收要求 |
 | [知识检索评估](../features/knowledge-base/retrieval-evaluation.md) | 检索数据集、指标及评估方法 |