Dock: Layer Manager pallet, double-click to float / dock

- LAYERS opens the Layer Manager as a dockable pallet instead of a modal
  dialog with a darkened backdrop. It floats over the middle of the
  drawing the first time and keeps its place after that; LAYERS again
  (or its close button) hides it. The table keeps its natural width and
  scrolls sideways when the pallet is narrower, and the Name column
  divider now drags through the dock's pointer capture. Ctrl+A selects
  all layers while a layer row is selected in the open pallet.
- The Layer Manager is listed in the tab-row pallet menu like the others.
- Double-clicking a docked title bar floats the panel beside its edge;
  double-clicking a floating title bar docks the panel on the side its
  title bar faces.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013RyGiMXcsf9HTKfqDxaQGt

src/app/update/dialog.rs

@@ -592,6 +592,38 @@ pub(super) fn on_ribbon_tool_click(&mut self, tool_id: String, event: ModuleEven
                 self.dock_title_hover = id;
                 iced::Task::none()
             }
+            DockMsg::FloatOut(id) => {
+                // Float beside the edge it was docked on, near the top.
+                let (ww, _) = self.dock_workspace_size();
+                let (w, h) = self.dock_float_size(id);
+                let x = match self.dock.location(id) {
+                    Some((DockSide::Right, _)) => {
+                        ww - self.dock_column_width(DockSide::Right) - w - 60.0
+                    }
+                    _ => self.dock_column_width(DockSide::Left) + 40.0,
+                };
+                self.dock_dragging = None;
+                self.dock_drag_target = None;
+                if self.dock.float(FloatPanel {
+                    id,
+                    x: x.max(0.0),
+                    y: 40.0,
+                    w,
+                    h,
+                }) {
+                    self.save_config();
+                }
+                iced::Task::none()
+            }
+            DockMsg::DockTo(id, side) => {
+                self.dock_dragging = None;
+                self.dock_drag_target = None;
+                if self.dock.dock(id, side, usize::MAX) {
+                    self.dock_expanded = Some(id);
+                    self.save_config();
+                }
+                iced::Task::none()
+            }
             DockMsg::TabMenu(slot) => {
                 self.dock_tab_menu = slot;
                 iced::Task::none()
@@ -666,6 +698,10 @@ pub(super) fn on_ribbon_tool_click(&mut self, tool_id: String, event: ModuleEven
                         self.show_properties = false;
                         self.ribbon.set_properties(false);
                     }
+                    PanelId::Layers => {
+                        self.show_layers = false;
+                        self.ribbon.deactivate_tool_if("LAYERS");
+                    }
                 }
                 if self.dock_expanded == Some(id) {
                     self.dock_expanded = None;
@@ -749,6 +785,11 @@ pub(super) fn on_ribbon_tool_click(&mut self, tool_id: String, event: ModuleEven
                             from_left,
                         );
                     }
+                } else if self.layer_col_dragging {
+                    if let Some(last) = self.dock_drag_last {
+                        self.layer_name_col_w =
+                            (self.layer_name_col_w + point.x - last.x).clamp(60.0, 640.0);
+                    }
                 } else if let Some(id) = self.dock_resizing {
                     if let Some(last) = self.dock_drag_last {
                         let dx = point.x - last.x;
@@ -768,6 +809,7 @@ pub(super) fn on_ribbon_tool_click(&mut self, tool_id: String, event: ModuleEven
                     || self.dock_resizing.is_some()
                     || self.dock_split_drag.is_some()
                     || self.dock_float_resizing.is_some()
+                    || self.layer_col_dragging
                 {
                     self.dock_drag_last = Some(point);
                 }
@@ -806,6 +848,7 @@ pub(super) fn on_ribbon_tool_click(&mut self, tool_id: String, event: ModuleEven
                 self.xref_col_drag = None;
                 self.xref_col_last = None;
                 self.xref_split_drag = false;
+                self.layer_col_dragging = false;
                 iced::Task::none()
             }
         }
@@ -835,6 +878,10 @@ pub(super) fn on_ribbon_tool_click(&mut self, tool_id: String, event: ModuleEven
             PanelId::PointCloudManager => self.pc_manager.show = true,
             PanelId::Count => self.set_count_palette(true),
             PanelId::SheetSetManager => self.show_sheet_set_manager(true),
+            PanelId::Layers => {
+                self.sync_ribbon_layers();
+                self.show_layers = true;
+            }
         }
         self.dock_expanded = Some(id);
         iced::Task::none()
@@ -871,6 +918,7 @@ pub(super) fn on_ribbon_tool_click(&mut self, tool_id: String, event: ModuleEven
             PanelId::PointCloudManager => self.pc_manager.show,
             PanelId::Count => self.count_palette.show,
             PanelId::SheetSetManager => self.sheet_set.show,
+            PanelId::Layers => self.show_layers,
         }
     }
 
@@ -2108,6 +2156,35 @@ mod tests {
         assert_eq!(app.dock_tab_menu, Some((DockSide::Left, 0)));
     }
 
+    #[test]
+    fn layers_command_opens_a_floating_pallet_and_toggles_it_closed() {
+        use crate::ui::dock::PanelId;
+        let mut app = dock_app();
+        let _ = app.update(Message::ToggleLayers);
+        assert!(app.show_layers);
+        assert!(app.active_modal.is_none(), "no modal backdrop");
+        let f = app.dock.float_rect(PanelId::Layers).expect("floats on first use");
+        assert!(f.x > 0.0 && f.y >= 0.0);
+        let _ = app.update(Message::ToggleLayers);
+        assert!(!app.show_layers);
+        // Its place is kept for next time.
+        assert!(app.dock.float_rect(PanelId::Layers).is_some());
+    }
+
+    #[test]
+    fn dock_double_clicks_float_and_dock_panels() {
+        use crate::app::config::DockSide;
+        use crate::ui::dock::{DockMsg, PanelId};
+        let mut app = dock_app();
+        let _ = app.on_dock(DockMsg::FloatOut(PanelId::Properties));
+        assert!(app.dock.left.is_empty());
+        let f = app.dock.float_rect(PanelId::Properties).expect("floating");
+        assert!(f.x > 0.0, "floats clear of the left edge");
+        let _ = app.on_dock(DockMsg::DockTo(PanelId::Properties, DockSide::Right));
+        assert!(app.dock.floating.is_empty());
+        assert_eq!(app.dock.location(PanelId::Properties), Some((DockSide::Right, 1)));
+    }
+
     #[test]
     fn dock_tab_group_resize_applies_to_every_tab() {
         use crate::app::config::DockSide;