refactor: group ui/ style+popup dirs, rename cmd_result driver

- Group the flat src/ui/ dir: move the 9 style editors into ui/style/
  (dimstyle, mleaderstyle, mlstyle, plotstyle, textstyle, tablestyle,
  point_style, style_list, style_manager) and the 6 popups into
  ui/popup/ (cycle, isolate, scale, selection_filter, snap, units).
  Call sites repointed to crate::ui::style::/crate::ui::popup::; no
  compat re-exports. ui/ root drops from 36 to 21 files.
- Rename app/cmd_result.rs -> app/command_driver.rs: the file is the
  StepInput->feed_command driver, not the CmdResult type (which lives
  in command.rs). Name now matches contents.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/ui/mod.rs

@@ -6,37 +6,24 @@ pub mod about;
 pub mod app_menu;
 pub mod color_select;
 pub mod command_line;
-pub mod cycle_popup;
-pub mod dimstyle;
 pub mod icons;
-pub mod isolate_popup;
 pub mod layers;
 pub mod layout_manager;
-pub mod mleaderstyle;
-pub mod mlstyle;
 pub mod modal;
 pub mod open_progress;
 pub mod overlay;
 pub mod page_setup;
-pub mod plotstyle;
 pub mod plugin_manager;
-pub mod point_style;
+pub mod popup;
 pub mod properties;
 pub mod ribbon;
-pub mod scale_popup;
-pub mod selection_filter_popup;
 pub mod side_toolbar;
 pub mod shortcuts;
-pub mod snap_popup;
 pub mod statusbar;
 pub mod statusbar_config;
 pub mod statusbar_menu;
-pub mod style_list;
-pub mod style_manager;
-pub mod tablestyle;
+pub mod style;
 pub mod text_util;
-pub mod textstyle;
-pub mod units_popup;
 pub mod update_notice;
 
 pub use app_menu::AppMenu;