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 <noreply@anthropic.com>

src/ui/popup/scale_popup.rs

@@ -0,0 +1,132 @@
+//! Scale picker dropdown — annotation scale (model space) or viewport scale (paper space).
+//!
+//! Rendered as a floating overlay above the status bar, same pattern as snap_popup.
+
+use iced::widget::{button, column, container, mouse_area, row, text};
+use iced::{Background, Border, Color, Element, Fill, Length, Padding, Theme};
+
+use crate::app::Message;
+
+/// Full-screen overlay: transparent click-catcher + scale list panel pinned bottom-right.
+///
+/// - `is_model`: true = model space (dispatches SetAnnotationScale), false = paper space (SetViewportScale).
+/// - `current_anno_scale`: current annotation_scale from Scene (used to highlight active row in model space).
+/// - `viewport_scale`: current effective vp scale, view_height-first (used to highlight in paper space).
+/// - `file_scales`: scale list read from the drawing (`ACAD_SCALELIST`). Only
+///   scales actually stored in the file are shown; the picker never injects
+///   scales of its own.
+pub fn scale_popup_overlay(
+    is_model: bool,
+    current_anno_scale: f32,
+    viewport_scale: Option<f64>,
+    file_scales: Vec<(String, f32, f64)>,
+) -> Element<'static, Message> {
+    let rows: Vec<Element<'static, Message>> = file_scales
+        .into_iter()
+        .map(|(label, anno_scale, vp_scale)| {
+            let active = if is_model {
+                (current_anno_scale - anno_scale).abs() < 0.001 * current_anno_scale.max(0.001)
+            } else {
+                viewport_scale
+                    .map(|vs| (vs - vp_scale).abs() < 0.001 * vp_scale.max(0.001))
+                    .unwrap_or(false)
+            };
+            let msg = if is_model {
+                Message::SetAnnotationScale(anno_scale)
+            } else {
+                Message::SetViewportScale(vp_scale)
+            };
+            scale_row(label, active, msg)
+        })
+        .collect();
+
+    let panel = container(column(rows))
+        .style(|_: &Theme| container::Style {
+            background: Some(Background::Color(PANEL_BG)),
+            border: Border {
+                color: PANEL_BORDER,
+                width: 1.0,
+                radius: 3.0.into(),
+            },
+            ..Default::default()
+        })
+        .width(Length::Fixed(120.0));
+
+    let positioned = container(panel)
+        .align_right(Fill)
+        .align_bottom(Fill)
+        .padding(Padding {
+            bottom: 27.0,
+            right: 4.0,
+            top: 0.0,
+            left: 0.0,
+        })
+        .width(Fill)
+        .height(Fill);
+
+    mouse_area(positioned)
+        .on_press(Message::CloseScalePopup)
+        .into()
+}
+
+fn scale_row(label: String, active: bool, msg: Message) -> Element<'static, Message> {
+    let check = crate::ui::icons::check_cell(active, CHECK_COLOR);
+
+    let lbl = text(label)
+        .size(11)
+        .color(if active { LABEL_ON } else { LABEL_OFF });
+
+    let content = row![check, lbl].spacing(6).align_y(iced::Center);
+
+    button(content)
+        .on_press(msg)
+        .style(|_: &Theme, status| button::Style {
+            background: Some(Background::Color(match status {
+                button::Status::Hovered => ROW_HOVER,
+                _ => Color::TRANSPARENT,
+            })),
+            ..Default::default()
+        })
+        .width(Fill)
+        .padding([4, 10])
+        .into()
+}
+
+// ── Colours ───────────────────────────────────────────────────────────────
+
+const PANEL_BG: Color = Color {
+    r: 0.15,
+    g: 0.15,
+    b: 0.15,
+    a: 1.0,
+};
+const PANEL_BORDER: Color = Color {
+    r: 0.32,
+    g: 0.32,
+    b: 0.32,
+    a: 1.0,
+};
+const ROW_HOVER: Color = Color {
+    r: 0.22,
+    g: 0.22,
+    b: 0.22,
+    a: 1.0,
+};
+const CHECK_COLOR: Color = Color {
+    r: 0.35,
+    g: 0.75,
+    b: 1.00,
+    a: 1.0,
+};
+const LABEL_ON: Color = Color {
+    r: 0.92,
+    g: 0.92,
+    b: 0.92,
+    a: 1.0,
+};
+const LABEL_OFF: Color = Color {
+    r: 0.65,
+    g: 0.65,
+    b: 0.65,
+    a: 1.0,
+};