fix: refresh magic notes after external updates

Subscribe the open Magic Notes workspace to committed database changes from desktop and Agent/MCP writes. Preserve selections and unsaved drafts during refresh and external deletion.

File-level commit includes existing runtime edits in shared files; their remaining dependencies are still in the working tree.

Release note: Magic Notes now updates automatically after Agent/MCP edits while preserving your selection and unsaved drafts.

docs/features/magic-notes/README.md

@@ -0,0 +1,18 @@
+# Magic Notes
+
+Magic Notes is the local notes, checklist and AI-comment workbench. Desktop
+actions and authorized Agent/MCP tools write to the same desktop SQLite store.
+The open workbench subscribes to successful writes so users can see external
+changes without leaving the page or clicking a refresh button.
+
+## Documents
+
+- [Technical design](./technical-design.md): database notifications, process
+  boundaries, refresh lifecycle and regression coverage.
+- [Progress](./progress.md): implementation and validation evidence.
+- [UI design system](../../../UI-DESIGN.md#137-魔法笔记): authoritative workbench
+  interaction rules, including selection and draft preservation.
+
+An entry is a saved rich-text record within a note. A todo is a checklist item
+derived from an entry. An unsaved draft belongs to the open editor; it is not
+written to storage by a background refresh.