Selection tools on the right-edge toolbar instead of contextual tabs

The PDF Underlay and External Reference ribbon tabs are gone. While only
PDF underlays are selected their tools (Display in Monochrome, Create
Clipping Boundary, Remove Clipping, Show Underlay, Enable Snap, External
References, Edit Layers, Import As Objects) sit on the right-edge toolbar,
the switches drawn as on while on; while only xrefs are selected the xref
tools do. Contrast and fade stay in Properties. Toolbar tooltips are
translated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ui/side_toolbar.rs

@@ -26,6 +26,8 @@ fn icon_el(icon: IconKind) -> Element<'static, Message> {
 }
 
 fn tip_panel(label: &'static str) -> Element<'static, Message> {
+    // Ribbon labels break over two lines; a tooltip reads them on one.
+    let label = crate::t!(label).replace('\n', " ");
     container(text(label).size(11))
         .padding([2, 6])
         .style(|theme: &Theme| {
@@ -48,12 +50,21 @@ fn tip_panel(label: &'static str) -> Element<'static, Message> {
 /// centred over the canvas. Returns `None` when `tools` is empty so the caller
 /// can skip pushing an overlay.
 pub fn view(tools: &[ToolDef]) -> Option<Element<'static, Message>> {
+    view_with_active(tools, &|_| false)
+}
+
+/// As [`view`], with the tools `active` names drawn as switched on.
+pub fn view_with_active(
+    tools: &[ToolDef],
+    active: &dyn Fn(&str) -> bool,
+) -> Option<Element<'static, Message>> {
     if tools.is_empty() {
         return None;
     }
 
     let mut col = column![].spacing(4).align_x(iced::Center);
     for t in tools {
+        let on = active(t.id);
         let btn = button(icon_el(t.icon))
             .on_press(Message::RibbonToolClick {
                 tool_id: t.id.to_string(),
@@ -61,18 +72,22 @@ pub fn view(tools: &[ToolDef]) -> Option<Element<'static, Message>> {
             })
             .width(Length::Fixed(BTN_SIZE))
             .height(Length::Fixed(BTN_SIZE))
-            .style(|theme: &Theme, status| {
+            .style(move |theme: &Theme, status| {
                 let palette = theme.palette();
                 let hovered = matches!(
                     status,
                     button::Status::Hovered | button::Status::Pressed
                 );
                 button::Style {
-                background: hovered
-                    .then_some(Background::Color(palette.background.strong.color)),
+                background: if on {
+                    Some(Background::Color(palette.primary.weak.color))
+                } else {
+                    hovered.then_some(Background::Color(palette.background.strong.color))
+                },
                 border: Border {
                     radius: 3.0.into(),
-                    ..Default::default()
+                    color: palette.primary.base.color,
+                    width: if on { 1.0 } else { 0.0 },
                 },
                 text_color: palette.background.base.text,
                 ..Default::default()