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/features/knowledge-base/progress.md

@@ -16,6 +16,36 @@
 
 ## 验证证据
 
+### 2026-09-13 检索路径与绑定查询简化
+
+对 `3b560c9..ca4a58c` 的复查发现三处与本功能相关的实现问题，已按 KISS 与性能优先修正：
+
+| 修正项 | 修正前行为 | 修正后行为 |
+| --- | --- | --- |
+| 生产检索入口 | 对话检索复用 `testRetrieval`，把用户问题传入 `testQuery`，并对 RAGFlow 额外发一次 detail 请求 | 新增 `ExternalKnowledgeService.retrieve` 作为生产路径，只发一次检索请求；能力预检仅保留在 `testRetrieval` |
+| 配置变更检测 | 5 处 `JSON.stringify` 前后快照对比，抛出 `EXTERNAL_KB_CONFIG_CHANGED` | 全部删除，改由既有 `AbortController` 取消覆盖；被取消的探测抛 `EXTERNAL_KB_CANCELLED` 且不写回探测结果 |
+| 绑定查询 | `requireLibrary`（30+ 调用点，其中一处在循环内）与 `getKnowledgeSnapshot` 每次全表 `listBindings()` | 新增 `getBinding`/`hasBinding`/`getBindingsForInstance` 主键查询；快照改为单次 `Map` 构建 |
+
+修正过程中被测试拦下两次行为回退，已记录为当前不变量：
+
+- 被取消的连接测试必须抛出且不写回 `probeStatus`，不能记为 `failed`；用户停用实例不等于探测失败。
+- `testRetrieval` 的 RAGFlow 能力预检必须与检索共用绑定配置的 `requestTimeoutMs`，不能各自计时。
+
+同时删除确认无生产引用的死代码：`probeStatus` 的 `'healthy'` 取值、`external.transportConfirm`
+与 `external.states` 的 `remote-missing`/`config-invalid` 文案、`KnowledgeService.searchHybridMany`、
+`ExternalKnowledgeRemoteResult.sourceUrl`。`externalKnowledgeLocatorSchema` 的 `sourceUrl`
+保留，因为它解析已持久化的引用数据。
+
+| 验证 | 结果 |
+| --- | --- |
+| `npx vitest run src/main/knowledge src/main/agent/knowledge-mcp-gateway.test.ts` | 21 个文件通过、1 个跳过；288 项通过、1 项跳过 |
+| `npm test` | 348 个文件通过、9 个跳过；4,088 项通过、66 项跳过 |
+| `npm run typecheck`、`npm run lint` | 通过 |
+
+`npm test` 的唯一失败为 `src/main/agent/opencode-runtime-lifecycle.test.ts:120`
+（"Matcher did not succeed in time"）。已用 `git stash` 在同一 `HEAD` 上复现同样失败，
+确认早于本次修正且与知识库无关，未计入上表。
+
 ### 2026-09-13 当前工作区实现与分组验证
 
 三家 Provider 已通过生产服务、本机 HTTP MCP 与生产 IPC 的短答案生成检查，Dify 另已