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.

src/preload/index.ts

@@ -1604,6 +1604,12 @@ const desktopApi: DesktopApi = {
           handler
         )
     },
+    onChanged: (listener) => {
+      const handler = (): void => listener()
+      ipcRenderer.on(ipcChannels.magicNotesChanged, handler)
+      return () =>
+        ipcRenderer.removeListener(ipcChannels.magicNotesChanged, handler)
+    },
     onTodoStatusChanged: (listener) => {
       const handler = (): void => listener()
       ipcRenderer.on(ipcChannels.magicTodosStatusChanged, handler)