Four features the user asked for together: an About dialog (version, build
timestamp, settings path), a shortcut overview covering the keyboard and the
mouse, a fourteen-page help window, and a status bar split into a short glance
line plus a details popover so the plot's own row stops being crowded.
Records one deviation from the approved design: keyboard zoom-x/zoom-y use
ctrl/alt rather than shift, because `+` *is* shift+`=` on the common layouts and
a bare zoom-in therefore already arrives with Shift set.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
