- Optional project pane: a directory tree from File → Open Folder…
  (Ctrl+Shift+K), toggled with Ctrl+Shift+P.
- Non-markdown files open in tabs: images (including SVG) are displayed
  read-only, binaries get a full hex editor with overwrite and insert modes,
  and everything else is editable text. 1 MB limit for text and binaries,
  16 MB for images.