feat(backthink/admin): ③b — rag/delete 真实现 + D1 推送出口钩子(自建优先→个推兜底) + api-reference 补 D2/D3/D5 补丁

- B5: POST /admin/rag/delete 真做(DeleteDocument→DeleteProject 级联删章节+索引清理, owner+审计, 200/404/500, 500降级兜底); users/iot scenarios+rules 诚实501(无用户表/IoT场景规则模型, 消息写明缺什么, 不伪造), 锁住 501+not_implemented
- D1: backthink/push_outlet.go PushExporter{Export}; pushOutlet 自建HTTP(2xx=送达, token仅Authorization头+error脱敏)优先→Getui兜底(未接入, 诚实日志'getui not integrated'+(false,nil)); backthink.Deps.Exporter → pusher.withExporter, Push 在WS/IM后 exportAsync(detached+5s超时, 失败仅日志, 不破坏现有投递, 限流不上报); config PushOutletConfig(PUSH_EXPORTER_* + GETUI_*占位)
- 前端 Rag.tsx/api.ts 删除后 reload + 类型; Docs/api-client v0.31 + api-reference(#23 owner/200-404, §8.4, 端点表PATCH/DELETE messages + pinned + messages?q=)
- 测试(push_outlet/admin_rag_delete/admin_honest501/knowledge store), 后端+前端build全绿+3平台交叉编译
- 刻意: Getui SDK 未接入(无SDK不硬造), 主人自建服务填 PUSH_EXPORTER_URL/TOKEN 即可

internal/services/backthink/backthink.go

@@ -82,6 +82,10 @@ type Deps struct {
 	Active ActiveClient
 	// IM is the IM bridge sink, used as the fallback when no active client is up.
 	IM IMAdapter
+	// Exporter mirrors a proactive message to the external push outlet (the
+	// owner's self-hosted unified push service, then Getui). Optional: nil
+	// disables the hook. It never blocks or breaks the Active/IM delivery.
+	Exporter PushExporter
 	// Gate is the proactive-push rate limiter. Nil builds a default from Config.
 	Gate PushGate
 	// DB is the SQLite handle for the think store. Required.
@@ -146,7 +150,7 @@ func New(cfg Config, deps Deps) (*Backthink, error) {
 	}
 	pusher := deps.Pusher
 	if pusher == nil {
-		pusher = newPusher(deps.Active, deps.IM, gate, log)
+		pusher = newPusher(deps.Active, deps.IM, gate, log).withExporter(deps.Exporter)
 	}
 
 	now := deps.Now