Fix redo shortcut on Windows, table rendering at doc start, and save on tab close

- Bind Mod-Shift-z to redo on all platforms (CodeMirror only binds it on Linux/macOS)
- Render tables based on editor focus so a note starting with a table is not shown as source
- Send the save request without waiting for the IndexedDB draft write, and flush on pagehide;
  Firefox could drop the last edit when a tab was closed right after typing
- Fall back to clipboardData.items when pasting images with an empty files list

web/src/editor/paste.ts

@@ -42,7 +42,11 @@ export function pasteImages(opts: PasteImagesOptions): Extension {
   }
   return EditorView.domEventHandlers({
     paste(e, view) {
-      const files = [...(e.clipboardData?.files ?? [])]
+      // 个别浏览器/来源只在 items 中提供图片
+      let files = [...(e.clipboardData?.files ?? [])]
+      if (!files.length) {
+        files = [...(e.clipboardData?.items ?? [])].filter((i) => i.kind === 'file').map((i) => i.getAsFile()).filter((f) => f !== null)
+      }
       if (!insert(view, files)) return false
       e.preventDefault()
       return true