Select Color: frameless gradient button, hex beside H/S/B, all Options swatches

- The gradient mode button is just its gradient, without a frame.
- In the gradient view H, S and B sit on the left and Hex on the right
  of one row; the nearest index colour moves to the row below.
- Every colour swatch in Options opens the Select Color panel: the six
  theme colours, crosshair, snap marker and command line text join the
  three viewport backgrounds. BgTarget becomes UiColor, and one
  color_swatch helper replaces the four hand-built swatches.

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_013rGmDUNr1hUf4zo1X3dak8

src/app/mod.rs

@@ -1577,12 +1577,17 @@ pub struct SaveOutcome {
     refreshed_preview: Option<Option<codec::Preview>>,
     result: Result<(), crate::io::SaveFailure>,
 }
-/// Which viewport background the interface colour picker is editing.
+/// Which Options colour the interface colour picker is editing.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum BgTarget {
-    Model,
-    Paper,
-    Desk,
+pub enum UiColor {
+    ModelBackground,
+    PaperBackground,
+    DeskBackground,
+    /// One of the six theme colours, by its row in Options.
+    Theme(usize),
+    Crosshair,
+    SnapMarker,
+    CommandText,
 }
 
 /// Where a colour chosen in the standalone palette window should be applied.
@@ -1607,8 +1612,8 @@ pub enum ColorPickTarget {
     LayerState(usize),
     /// The MText editor's selection (or global) colour.
     MText,
-    /// An Options viewport background (interface colour, true colour only).
-    Background(BgTarget),
+    /// An Options interface colour (true colour only).
+    Interface(UiColor),
 }
 
 /// Table records the clipboard entities depend on, snapshotted from the source

src/app/update/mod.rs

@@ -11061,7 +11061,7 @@ impl OpenCADStudio {
                 // the recent list.
                 if !matches!(
                     self.color_picker.as_ref().map(|picker| &picker.target),
-                    Some(crate::app::ColorPickTarget::Background(_))
+                    Some(crate::app::ColorPickTarget::Interface(_))
                 ) {
                     self.note_recent_color(color);
                 }

src/app/update/style.rs

@@ -1136,7 +1136,7 @@ impl OpenCADStudio {
     }
 
     pub(super) fn on_color_window_pick(&mut self, color: codec::types::Color) -> Task<Message> {
-        if let Some(crate::app::ColorPickTarget::Background(target)) = self
+        if let Some(crate::app::ColorPickTarget::Interface(target)) = self
             .color_picker
             .as_ref()
             .map(|picker| picker.target.clone())
@@ -1146,13 +1146,18 @@ impl OpenCADStudio {
                 return Task::none();
             };
             // Hand the result to the same handler the typed hex field uses, so
-            // the picker and the field cannot drift apart on validation,
-            // persistence or the MatchTheme fallback.
+            // the picker and the field cannot drift apart on validation or
+            // persistence.
             let hex = crate::app::config::rgb_to_hex([r, g, b]);
+            use crate::app::UiColor;
             return Task::done(match target {
-                crate::app::BgTarget::Model => Message::ModelSpaceBgChanged(hex),
-                crate::app::BgTarget::Paper => Message::PaperSpaceBgChanged(hex),
-                crate::app::BgTarget::Desk => Message::DeskSpaceBgChanged(hex),
+                UiColor::ModelBackground => Message::ModelSpaceBgChanged(hex),
+                UiColor::PaperBackground => Message::PaperSpaceBgChanged(hex),
+                UiColor::DeskBackground => Message::DeskSpaceBgChanged(hex),
+                UiColor::Theme(index) => Message::OptionsThemeColorChanged(index, hex),
+                UiColor::Crosshair => Message::CrosshairColorChanged(hex),
+                UiColor::SnapMarker => Message::SnapMarkerColorChanged(hex),
+                UiColor::CommandText => Message::CommandTextColorChanged(hex),
             });
         }
         if matches!(
@@ -1208,7 +1213,7 @@ impl OpenCADStudio {
             }
             // Handled before this match.
             Some(
-                crate::app::ColorPickTarget::PlotStyle | crate::app::ColorPickTarget::Background(_),
+                crate::app::ColorPickTarget::PlotStyle | crate::app::ColorPickTarget::Interface(_),
             ) => None,
             None => None,
         };