feat(ui): add dockable properties panel

Preserve panel width across left/right docking and persist resize, position, and auto-collapse preferences.

Refs #348
Refs #650

src/app/config.rs

@@ -27,6 +27,8 @@ pub struct AppConfig {
     pub start: StartConfig,
     /// Which status-bar pills the user has hidden.
     pub statusbar: StatusBarConfig,
+    /// Dock position, width and auto-collapse behavior of the Properties panel.
+    pub properties: PropertiesDockConfig,
     /// Add a newly selected annotation scale to existing annotative objects.
     pub annotation_auto_scale: i8,
     /// Ribbon collapse density.
@@ -44,6 +46,7 @@ impl Default for AppConfig {
             recent: RecentConfig::default(),
             start: StartConfig::default(),
             statusbar: StatusBarConfig::default(),
+            properties: PropertiesDockConfig::default(),
             annotation_auto_scale: -4,
             ribbon: RibbonConfig::default(),
             plot: PlotDialogState::default(),
@@ -51,6 +54,30 @@ impl Default for AppConfig {
     }
 }
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub enum DockSide {
+    Left,
+    Right,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Serialize, Deserialize)]
+#[serde(default)]
+pub struct PropertiesDockConfig {
+    pub side: DockSide,
+    pub width: f32,
+    pub auto_collapse: bool,
+}
+
+impl Default for PropertiesDockConfig {
+    fn default() -> Self {
+        Self {
+            side: DockSide::Left,
+            width: 250.0,
+            auto_collapse: false,
+        }
+    }
+}
+
 #[derive(Clone, PartialEq, Serialize, Deserialize)]
 #[serde(default)]
 pub struct UiThemeConfig {