feat: add file-backed canvas notes

Magic Notes previously supported rich-text records without a paged drawing or
PDF annotation workflow. Add the integrated PeopleLib Fabric and Quill editor
with flowing text, pen/highlighter, object transforms, images, paper templates,
PDF backgrounds with native text extraction, and raster PDF export. Saves are
manual; undo/redo remains scoped to an annotation page or Quill mode.

Analyze drafts, saved canvases and canvas-source todos with page images and
text when the default model supports images, or an explicitly labelled
text-only fallback. Keep successful saves when automatic analysis fails and
prevent MCP plain-text replacement of canvas records.

Move entry bodies and binary assets into local note files with schema 38
migration and verified readback. SQLite retains metadata, indexes, revisions,
todos and comments. Backups must coordinate SQLite and the adjacent notes
directory while writes are paused or the app is closed; no one-click backup
action is included.

Show a continuous record stream with independent collapsible record index and
AI pane, real first-page thumbnails, and scroll-only record navigation. Open a
blank text/canvas composer by default and reset it after creation. Protect
unsaved drafts and establish normalized editor baselines after saving so clean
records do not prompt again when leaving.

Validation: latest recorded focused run passed 149 tests across five files;
typecheck, lint and git diff --check passed. The prior user-reported full run
passed 4,713 tests before later corrections and UI changes; it is not a full
validation of this final snapshot. Tests were not rerun for this commit, as
requested; independent systematic review follows the commit.

Release note: Create paged notes with handwriting, flowing text and PDF
annotations, browse records through thumbnails, and request AI comments with
an explicit text-only fallback. Existing notes migrate to local file storage;
backups now need both the database and notes directory.

FEATURES.zh-CN.md

@@ -91,6 +91,8 @@
 - [x] **受控知识本体**：每个知识库可定义实体、关系、别名和端点约束，保留证据偏移、置信度和抽取来源，并显式提示图谱重建。
 - [x] **强制检索与引用上下文**：对话可按需或每次先检索，显示零结果、降级、失败与取消状态，并可查看引用上下文或安全打开来源。
 - [x] **魔法笔记 / Magic Notes**：提供本地优先的笔记与待办工作台、范围管理、编辑、筛选和受控 AI 评论。笔记从自适应卡片总览打开；独立待办页提供搜索、状态筛选、分组列表和直接勾选，宽屏列表稳定在左侧，任务说明、来源记录及 AI 评论在右侧同一区域显示，窄屏按需显示详情并提供返回列表。紧凑页签放在页头新建按钮左侧，筛选放在搜索右侧。打开原笔记再返回可恢复任务上下文；切换任务不会混入上一项的来源内容，读取失败使用应用通知并提供就地重试，来源缺失有明确提示。左侧入口可按设置显示未完成待办数量，创建、保存和评论结果使用统一应用通知。Agent / MCP 写入后，已打开的工作台自动更新，并保留当前选择与未保存草稿。
+- [x] **连续记录工作区**：笔记详情连续展示全部记录，左侧 168px 索引与右侧 AI 评论独立收起。每条画布记录显示真实首页缩略图、页数和时间，文字记录显示摘要；点击索引只滚动定位，保留当前编辑器和草稿。打开笔记就在标题下方显示空白输入区，保留文字/画布选择和保存操作；新增保存后清空，供下一条记录使用，旧记录通过编辑入口修改。空白输入区和保存后未再修改的记录返回时不提示；保存失败和真实修改仍受保护。窄屏索引使用折叠抽屉，AI 评论移至底部。
+- [x] **分页画布笔记**：已集成 PeopleLib Fabric + Quill 编辑器，支持跨页正文、笔迹、高亮、对象选择及变换、浮动文字、图片和纸张模板。PDF 可作为分页底版导入并提取原生文字；正文和批注可导出为栅格 PDF，导出文件不保留可搜索文字层。用户手动保存后，记录正文与二进制资源存入本地笔记文件，SQLite 保留元数据、索引、修订、待办和评论。备份须协调保存 SQLite 与笔记目录，产品无一键备份入口。撤销/重做限当前批注页或 Quill 模式，不提供全局文档撤销、无限画布或 PNG 下载按钮。草稿、已保存记录和来源为画布的待办按默认模型图像输入能力使用页面图像加文字，或明确标注仅文字降级；纯视觉记录/草稿需要支持图像输入的模型。即时评论模式提供手动画布分析，保存后自动分析失败不阻断或回滚保存。提取文字不变时保留文字评论；布局变化使视觉评论失效，并在保存后自动评论模式下重新分析。MCP 禁止以纯文字覆写画布记录。实现已完成，最终验证状态见[功能进展](./docs/features/magic-notes/progress.md)。
 - [ ] **MCP Server Control Plane**（规划中）：统一 MCP 生命周期、健康检查、重连、Schema 缓存、隔离、审批和审计。
 - [ ] **可追溯笔记摘录与 AI 编辑**（规划中）：从对话、知识和网页收集带来源的摘录，并提供需确认的总结、改写和整理操作。