feat: add persistent document handling and protect note drafts

Add HTTP PaddleOCR-VL settings and shared document previews for chat and knowledge imports. Preserve attachment originals and parsed assets across drafts, messages and queues; support explicit image OCR, selecting document images into a conversation draft, and restoring queued input for editing.

Protect unsaved note bodies and titles during navigation and asynchronous updates. Match canvas analysis to source revisions, invalidate affected comments, preserve annotations during pagination, and provide a resizable record index with saved width preferences.

Existing OCR settings retain local behavior. Historical attachments without saved originals are not reconstructed. Advanced OCR options depend on the configured service; image sending depends on the effective model and Runtime.

Validation: full typecheck and lint passed; 477 focused tests passed across 12 files; staged whitespace checks passed. The full repository suite was not rerun for this commit.

Release note: Keep note drafts safe while switching workspaces, resize the record index, and revisit saved document attachments with OCR previews and selected images in chat.

docs/features/application-tool-navigation/README.md

@@ -117,3 +117,4 @@ Notion 收藏和 VS Code Profiles，当前版本已移除场景工具包与快
 - [助手工作栏多终端页签 PRD](../assistant-workbar/terminal-tabs-prd.md)
 - [智能心跳 PRD](../smart-heartbeat/prd.md)
 - [知识库功能文档](../knowledge-base/README.md)
+- [文档解析入口与职责](../document-processing/ui-design.md#11-入口与职责)：全局 OCR 配置、附件与知识文档操作的目标分工；不新增应用中心成员，本机推理监控不管理 HTTP OCR 服务。