refactor(ribbon): single dock predicate, drop dead layer_names mirror

The edge-stack closure duplicated dock_panel_visible arm-for-arm; it now delegates (tab is provably the active tab at that site). Ribbon.layer_names was written but never read outside one test; deleted, test reads via layer_infos. Faces and combo-refresh sub-items investigated and dropped (already unified upstream; no live stale path). Tests: dock visibility parity pins incl. Start-tab. Full suite: 2046 passed / 0 failed / 25 ignored, zero warnings.

src/app/plugin_host.rs

@@ -9701,7 +9701,7 @@ step('undo_move', lambda: M.move([u], (0, 0, 0), (7, 0, 0)))
 
         // Verify COGO_LINES does not exist initially
         assert!(!app.tabs[0].scene.document.layers.contains("COGO_LINES"));
-        assert!(!app.ribbon.layer_names.contains(&"COGO_LINES".to_string()));
+        assert!(!app.ribbon.layer_infos.iter().any(|l| l.name == "COGO_LINES"));
 
         // 1. Add entity via HostSession (simulating plugin add_entity / add_line)
         {
@@ -9714,7 +9714,7 @@ step('undo_move', lambda: M.move([u], (0, 0, 0), (7, 0, 0)))
 
         // Verify layer is created in document AND refreshed in ribbon + layer panel
         assert!(app.tabs[0].scene.document.layers.contains("COGO_LINES"));
-        assert!(app.ribbon.layer_names.contains(&"COGO_LINES".to_string()),
+        assert!(app.ribbon.layer_infos.iter().any(|l| l.name == "COGO_LINES"),
             "Ribbon layers should contain COGO_LINES after add_entity");
         assert!(app.tabs[0].layers.layers.iter().any(|l| l.name == "COGO_LINES"),
             "Layer panel should contain COGO_LINES after add_entity");
@@ -9726,7 +9726,7 @@ step('undo_move', lambda: M.move([u], (0, 0, 0), (7, 0, 0)))
 
         // Verify SURVEY_TRAVERSE layer is created and refreshed in ribbon + layer panel
         assert!(app.tabs[0].scene.document.layers.contains("SURVEY_TRAVERSE"));
-        assert!(app.ribbon.layer_names.contains(&"SURVEY_TRAVERSE".to_string()),
+        assert!(app.ribbon.layer_infos.iter().any(|l| l.name == "SURVEY_TRAVERSE"),
             "Ribbon layers should contain SURVEY_TRAVERSE after commit_entity");
         assert!(app.tabs[0].layers.layers.iter().any(|l| l.name == "SURVEY_TRAVERSE"),
             "Layer panel should contain SURVEY_TRAVERSE after commit_entity");

src/app/update/mod.rs

@@ -11233,6 +11233,57 @@ mod anno_scale_toggle_tests {
     }
 }
 
+#[cfg(test)]
+mod dock_visibility_tests {
+    // #57: one visibility predicate for edge rendering and drag math. Pins
+    // the full 8-panel table so a newly added panel cannot silently diverge
+    // (behavior-preserving dedup: passes before and after by construction).
+    use crate::app::OpenCADStudio;
+    use crate::ui::dock::PanelId;
+
+    const ALL: [PanelId; 8] = [
+        PanelId::Properties,
+        PanelId::BlockPalette,
+        PanelId::ExternalReferences,
+        PanelId::Browser,
+        PanelId::NodeGraph,
+        PanelId::PointCloudManager,
+        PanelId::Count,
+        PanelId::SheetSetManager,
+    ];
+
+    #[test]
+    fn dock_panel_visible_covers_every_panel() {
+        let mut app = OpenCADStudio::new_for_test();
+        app.automation_op(r#"{"op":"new"}"#);
+        app.show_properties = true;
+        app.show_block_palette = true;
+        app.show_external_references = true;
+        app.show_browser = true;
+        app.show_node_graph = true;
+        app.pc_manager.show = true;
+        app.count_palette.show = true;
+        app.sheet_set.show = true;
+        for id in ALL {
+            assert!(app.dock_panel_visible(id), "{id:?} must be visible");
+        }
+        app.clean_screen = true;
+        for id in ALL {
+            assert!(!app.dock_panel_visible(id), "{id:?} must hide on clean screen");
+        }
+    }
+
+    #[test]
+    fn dock_panel_hidden_on_start_tab() {
+        // Fresh app, no drawing opened: the welcome tab shows no panels.
+        let app = OpenCADStudio::new_for_test();
+        assert!(app.tabs[app.active_tab].is_start);
+        for id in ALL {
+            assert!(!app.dock_panel_visible(id), "{id:?} must hide on Start");
+        }
+    }
+}
+
 #[cfg(test)]
 mod free_text_entry_tests {
     //! The free-form text prompts (table cell content, TEXT / MTEXT bodies)

src/app/view/mod.rs

@@ -1885,20 +1885,10 @@ bg={bg_ms:.1}ms n={view_count}"
         // view. Auto-collapsing (pinned) panels that aren't being hovered
         // reduce to a rail sharing 1/N of the edge column's height; the
         // hovered or unpinned panel expands to the full column height on top.
+        // Single source of truth with dock_visible_len (#57): one new panel
+        // updated in only one place used to break drag math vs rendering.
         let visible_panel = |id: crate::ui::dock::PanelId| -> bool {
-            if tab.is_start || self.clean_screen {
-                return false;
-            }
-            match id {
-                crate::ui::dock::PanelId::Properties => self.show_properties,
-                crate::ui::dock::PanelId::BlockPalette => self.show_block_palette,
-                crate::ui::dock::PanelId::ExternalReferences => self.show_external_references,
-                crate::ui::dock::PanelId::Browser => self.show_browser,
-                crate::ui::dock::PanelId::NodeGraph => self.show_node_graph,
-                crate::ui::dock::PanelId::PointCloudManager => self.pc_manager.show,
-                crate::ui::dock::PanelId::Count => self.count_palette.show,
-                crate::ui::dock::PanelId::SheetSetManager => self.sheet_set.show,
-            }
+            self.dock_panel_visible(id)
         };
         let edge_stack = |side: crate::app::config::DockSide| -> Option<Element<'_, Message>> {
             let ids: Vec<crate::ui::dock::PanelId> = match side {

src/ui/ribbon/mod.rs

@@ -73,7 +73,6 @@ pub struct Ribbon {
     /// shows this tool on its button, defaulting to the panel's first tool.
     last_panel_tool: HashMap<&'static str, &'static str>,
     last_cmd: HashMap<&'static str, &'static str>,
-    pub layer_names: Vec<String>,
     pub active_layer: String,
     pub layer_infos: Vec<LayerInfo>,
     /// Live filter for the layer dropdown's search box (#343). Cleared on
@@ -189,7 +188,6 @@ impl Ribbon {
             last_panel_tool: HashMap::default(),
             last_cmd: HashMap::default(),
             // Empty until a document is open — populated by sync_ribbon_layers.
-            layer_names: vec![],
             active_layer: String::new(),
             layer_infos: vec![],
             layer_filter: String::new(),
@@ -285,7 +283,6 @@ impl Ribbon {
 
     pub fn set_layers(&mut self, infos: Vec<LayerInfo>, active: &str) {
         self.active_layer = active.to_string();
-        self.layer_names = infos.iter().map(|l| l.name.clone()).collect();
         self.layer_infos = infos;
     }