Frames: state-following ribbon list, DWF/DGN frames, image frame encoding and profile, frame-only picking

- The Frames list shows the drawing's frame state (hide / display and plot /
  display but not plot / frames vary), follows commands, undo and document
  switches, and lists the mixed state as a disabled item.
- DWFFRAME and DGNFRAME are frame variables of their own, kept in the header,
  and FRAME sets them with the others.
- Out-of-range frame values say "Requires an integer between 0 and 2." and
  ask again; a set value reports "Regenerating model.".
- IMAGEFRAME is stored in the image variables as bits (2 is written as 3) and
  a drawing without them uses the profile value, which setting IMAGEFRAME
  updates and the settings file keeps.
- Raster images, PDF underlays and wipeouts are picked on their frame only;
  underlay snap geometry is never picked.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/modules/view/plot_window.rs

@@ -61,6 +61,7 @@ impl CadCommand for PlotWindowCommand {
             world_width: 0.0,
             depth_override: None,
             display_visible: true,
+            snap_only: false,
             plot_visible: true,
             fill_is_3d: false,
             fill_is_2d_solid: false,