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/runtime/knowledge/store.go

@@ -15,9 +15,9 @@
 // stores it as a project plus its chapters, making it text/keyword-searchable
 // immediately. Semantic/vector embedding of an imported document is a graceful
 // no-op here (this data source holds no vector index); the existing semantic path
-// still ranks project-linked memories via the retriever. Deletion remains
-// unimplemented (M10) and returns ErrWriteUnsupported so the admin handler
-// answers honestly instead of fabricating a success.
+// still ranks project-linked memories via the retriever. DeleteDocument removes a
+// document (its project entry and, in one transaction, every chapter that
+// references it) so the import/delete pair is a real round-trip.
 package knowledge
 
 import (
@@ -36,10 +36,15 @@ import (
 	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/memory/projectindex"
 )
 
-// ErrWriteUnsupported is returned by DeleteDocument. Deletion is milestone M10;
-// the admin handler maps it to a clear 501 so the frontend can explain rather
-// than show a placeholder alert.
-var ErrWriteUnsupported = errors.New("knowledge: delete is not implemented in this milestone")
+// ErrWriteUnsupported is returned by a knowledge store implementation that does
+// not support document deletion. *Store implements DeleteDocument, so it never
+// returns this; it remains for alternate/degraded implementations the admin
+// handler maps to a clear 501 rather than a fabricated success.
+var ErrWriteUnsupported = errors.New("knowledge: delete is not supported by this store")
+
+// ErrDocumentNotFound is returned by DeleteDocument when the id is blank or no
+// knowledge document (project-index entry) carries it.
+var ErrDocumentNotFound = errors.New("knowledge: document not found")
 
 // defaultTopK bounds the semantic retrieval path.
 const defaultTopK = 8
@@ -322,10 +327,27 @@ func (s *Store) IndexDocument(ctx context.Context, doc Doc) error {
 	return nil
 }
 
-// DeleteDocument is not implemented in this milestone. It returns
-// ErrWriteUnsupported so the handler answers honestly (delete = M10).
-func (s *Store) DeleteDocument(_ context.Context, _ string) error {
-	return ErrWriteUnsupported
+// DeleteDocument removes a knowledge document: the project-index entry and, in
+// the same transaction, every chapter that references it (projectindex.DeleteProject
+// cascades the chunk cleanup). It returns ErrDocumentNotFound for a blank id or
+// one with no project entry, and an error when no project index is wired (there
+// is nowhere to delete from, so a fabricated success is never returned).
+func (s *Store) DeleteDocument(ctx context.Context, id string) error {
+	docID := strings.TrimSpace(id)
+	if docID == "" {
+		return fmt.Errorf("knowledge: delete document: %w", ErrDocumentNotFound)
+	}
+	if s.projects == nil {
+		return errors.New("knowledge: delete document: project index store is not configured")
+	}
+	if err := s.projects.DeleteProject(ctx, docID); err != nil {
+		if errors.Is(err, projectindex.ErrProjectNotFound) {
+			return fmt.Errorf("knowledge: delete document %q: %w", docID, ErrDocumentNotFound)
+		}
+		return fmt.Errorf("knowledge: delete document %q: %w", docID, err)
+	}
+	s.log.Info("deleted document", "project", docID)
+	return nil
 }
 
 // maxChapterRunes bounds a single chapter's content length. Paragraphs longer