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/app/update/mod.rs

@@ -2703,7 +2703,7 @@ impl OpenCADStudio {
                 self.style_rename_start(kind, name);
                 // Focus the freshly-shown rename field so the user can type
                 // immediately after the double click.
-                iced::widget::operation::focus(crate::ui::style_list::rename_input_id())
+                iced::widget::operation::focus(crate::ui::style::style_list::rename_input_id())
             }
             Message::StyleRenameEdit(s) => {
                 self.style_rename_buf = s;