feat: add style selector comboboxes to Annotate ribbon tab

New StyleComboGroup RibbonItem renders a dropdown combobox for selecting
text style, dimension style, multileader style, or table style. Ribbon
groups in the Annotate tab now match the reference layout: each group
has a large tool on the left and a style combobox with tool rows on the
right.

Each combobox shows the active style name, opens a scrollable item list
on click, and has an optional "Manage…" row that fires the style manager
command (STYLE / DIMSTYLE / MLEADERSTYLE / TABLESTYLE).

Style state is synced from the document on every layer refresh via
sync_ribbon_styles(). RibbonStyleChanged message propagates selections
back to the acadrust document header and the active_mleader_style field.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/update.rs

@@ -1929,6 +1929,43 @@ impl H7CAD {
                 Task::none()
             }
 
+            Message::RibbonStyleChanged { key, name } => {
+                use crate::modules::StyleKey;
+                self.ribbon.close_dropdown();
+                match key {
+                    StyleKey::TextStyle => {
+                        self.ribbon.active_text_style = name.clone();
+                        let i = self.active_tab;
+                        let found = self.tabs[i].scene.document.text_styles.iter()
+                            .find(|s| s.name == name)
+                            .map(|ts| ts.handle);
+                        if let Some(h) = found {
+                            self.tabs[i].scene.document.header.current_text_style_handle = h;
+                            self.tabs[i].scene.document.header.current_text_style_name = name;
+                        }
+                    }
+                    StyleKey::DimStyle => {
+                        self.ribbon.active_dim_style = name.clone();
+                        let i = self.active_tab;
+                        let found = self.tabs[i].scene.document.dim_styles.get(&name)
+                            .map(|ds| ds.handle);
+                        if let Some(h) = found {
+                            self.tabs[i].scene.document.header.current_dimstyle_handle = h;
+                            self.tabs[i].scene.document.header.current_dimstyle_name = name;
+                        }
+                    }
+                    StyleKey::MLeaderStyle => {
+                        self.ribbon.active_mleader_style = name.clone();
+                        let i = self.active_tab;
+                        self.tabs[i].active_mleader_style = name;
+                    }
+                    StyleKey::TableStyle => {
+                        self.ribbon.active_table_style = name;
+                    }
+                }
+                Task::none()
+            }
+
             Message::PropLayerChanged(layer) => {
                 let i = self.active_tab;
                 let handles = self.property_target_handles(i);