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/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)