feat(ui): move full ACI palette to a separate "Select Color" window (#94)

The colour selector popup now lists only the named colours (ByLayer,
ByBlock, ACI 1-9) plus a "More…" entry. "More…" opens a standalone
"Select Color" window with the full 256-colour grid; picking there applies
to the originating field (dimension/multileader/table style) and closes
the window. Routed via a ColorPickTarget so one window serves every field.

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

src/ui/dimstyle.rs

@@ -1,6 +1,6 @@
 //! Dimension Style Manager window — fills the entire OS window.
 
-use crate::app::{DsField, Message};
+use crate::app::{ColorPickTarget, DsField, Message};
 use iced::widget::{
     button, checkbox, column, container, pick_list, row, scrollable, text, text_input, Space,
 };
@@ -308,6 +308,7 @@ pub fn view_window<'a>(
             },
             move |c| Message::DsEdit(f_sel.clone(), crate::ui::color_select::color_to_aci_string(c)),
             Message::DsColorMore(fld.clone()),
+            Message::OpenColorWindow(ColorPickTarget::DimStyle(fld.clone())),
         );
         row![lbl(label), selector]
             .spacing(8)