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.

README.md

@@ -53,7 +53,7 @@ current limitations.
 | Area | Available in GoodBuddy |
 | --- | --- |
 | Agent Runtimes | Direct model connections, OpenCode, Continue, and the preview DeepSeek Harness |
-| Data and execution | Local SQLite storage, read-only `Ask`, full-account `Execute`, and recorded tool activity |
+| Data and execution | Local SQLite and note-file storage, read-only `Ask`, full-account `Execute`, and recorded tool activity |
 | Knowledge | File, folder, and web imports with full-text, Chinese phrase, vector, and knowledge graph retrieval |
 | Desktop releases | Official Windows, macOS, and Linux builds for `x64` and `arm64`, plus an experimental LoongArch preview |
 | Integrations | Local or hosted model endpoints, custom MCP servers, WeChat ClawBot, WeCom, and DingTalk |
@@ -68,6 +68,15 @@ current limitations.
 
 ### Magic Notes and Smart Heartbeat
 
+Magic Notes displays a continuous record stream, with a narrow left index and
+independent right AI comments. Both panes can collapse; thumbnails scroll to a
+record while preserving drafts. It supports rich-text entries and paged canvases with flowing text,
+handwriting, highlights, images and PDF backgrounds. Import PDF text and export
+annotated pages as a raster PDF. Canvas saves are manual; AI comments use the
+default model's image-input capability, with an explicit text-only fallback when
+images are unsupported. See the [Magic Notes documentation](./docs/features/magic-notes/README.md)
+for behavior and final validation status.
+
 ![GoodBuddy Magic Notes](./docs/screenshots/GoodBuddy_MFSGeK0NoT.gif)
 
 ![GoodBuddy Smart Heartbeat](./docs/screenshots/smart-heartbeat.png)