feat(ui): shared colour selector used across all style editors (#94)

Add a reusable color_selector widget (ui/color_select.rs): a main-colour
dropdown plus a "more colours" button that expands the full 255-entry ACI
palette — the same design the properties panel uses. Replace the flat ACI
swatch rows added earlier in the dimension, multileader and table style
editors with it, wired through each editor's existing colour edit message
(the chosen colour is encoded as an ACI string) plus a per-field
palette-open toggle.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/dimstyle.rs

@@ -126,6 +126,8 @@ pub struct DimStyleValues<'a> {
     // Dropdown option lists shared by the arrowhead / linetype fields.
     pub block_opts: Vec<String>,
     pub lt_opts: Vec<String>,
+    /// Colour field whose expanded palette is currently open.
+    pub color_open: Option<DsField>,
 }
 
 fn tab_btn_style(active: bool) -> impl Fn(&Theme, button::Status) -> button::Style {
@@ -290,43 +292,24 @@ pub fn view_window<'a>(
         ("6", "Windows desktop"),
     ];
 
-    // ACI colour swatches (1-9) + ByLayer; reuses the existing DsEdit path
-    // (the chosen index is sent as the field's string value).
-    let color_row = move |label: &'static str, fld: DsField, val: &'a str| -> Element<'a, Message> {
-        let cur: i16 = val.trim().parse().unwrap_or(256);
-        let mut swatches = row![].spacing(2).align_y(iced::Center);
-        for aci in 1u8..=9 {
-            let c = acadrust::types::Color::from_index(aci as i16);
-            let (bg, _) = crate::ui::properties::acad_color_display(c);
-            let sel = cur == aci as i16;
-            swatches = swatches.push(
-                button(text("").width(16).height(14))
-                    .on_press(Message::DsEdit(fld.clone(), aci.to_string()))
-                    .style(move |_: &Theme, _| button::Style {
-                        background: Some(Background::Color(bg)),
-                        border: Border {
-                            color: if sel { Color::WHITE } else { Color::BLACK },
-                            width: if sel { 2.0 } else { 1.0 },
-                            radius: 2.0.into(),
-                        },
-                        ..Default::default()
-                    }),
-            );
-        }
-        // ByLayer (256) chip.
-        swatches = swatches.push(
-            button(text("ByLayer").size(10))
-                .on_press(Message::DsEdit(fld.clone(), "256".to_string()))
-                .style(move |_: &Theme, _| button::Style {
-                    border: Border {
-                        color: if cur == 256 { Color::WHITE } else { BORDER },
-                        width: if cur == 256 { 2.0 } else { 1.0 },
-                        radius: 2.0.into(),
-                    },
-                    ..Default::default()
-                }),
+    // Shared colour selector (main dropdown + "more" palette), reusing the
+    // existing DsEdit path (the chosen colour is sent as an ACI string).
+    let color_open = vals.color_open.clone();
+    let color_row = move |label: &'static str, fld: DsField, _val: &'a str| -> Element<'a, Message> {
+        let cur = crate::ui::color_select::aci_string_to_color(_val);
+        let open = color_open.as_ref() == Some(&fld);
+        let f_sel = fld.clone();
+        let selector = crate::ui::color_select::color_selector(
+            cur,
+            open,
+            crate::ui::color_select::ColorExtras {
+                by_layer: true,
+                by_block: true,
+            },
+            move |c| Message::DsEdit(f_sel.clone(), crate::ui::color_select::color_to_aci_string(c)),
+            Message::DsColorMore(fld.clone()),
         );
-        row![lbl(label), swatches]
+        row![lbl(label), selector]
             .spacing(8)
             .align_y(iced::Center)
             .into()