Preferences: the Tools Panel columns go through window.toolsDoubleColumn

The command takes `on` (default: toggle), and Preferences OK runs it with the
chosen state instead of setting the flag itself.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/dialogs.rs

@@ -3426,7 +3426,7 @@ pub fn confirm(app: &mut DesignApp) -> Result<Value, String> {
                 app.run("window.brightness", json!({"brightness": b}))?;
             }
             if d.fields.contains_key("toolsColumns") {
-                app.ui.tools_double_column = d.s("toolsColumns") == "double";
+                app.run("window.toolsDoubleColumn", json!({"on": d.s("toolsColumns") == "double"}))?;
             }
             if let Some(v) = d.n("uiScale") {
                 app.run("window.uiScale", json!({"scale": v / 100.0}))?;
@@ -7531,6 +7531,10 @@ mod tests {
         assert!(h.state().ui.dialog.is_none());
         assert_eq!(h.state().ui.brightness, Brightness::Dark);
         assert!(h.state().ui.tools_double_column);
+        // The same command the Window menu toggles, with an explicit state for Preferences.
+        assert_eq!(h.state_mut().run("window.toolsDoubleColumn", json!({"on": false})).unwrap(), json!(false));
+        assert_eq!(h.state_mut().run("window.toolsDoubleColumn", json!({"on": false})).unwrap(), json!(false), "set, not toggled");
+        assert_eq!(h.state_mut().run("window.toolsDoubleColumn", json!({})).unwrap(), json!(true), "toggled without `on`");
         // UI Size has a section of its own.
         open(h.state_mut());
         h.state_mut().ui.dialog.as_mut().unwrap().fields.insert("section".into(), json!("uiScaling"));

crates/ui-egui/src/menus.rs

@@ -291,7 +291,7 @@ pub const UI_COMMANDS: &[(&str, &str, Option<&str>, &str)] = &[
         None,
         "{open?: true, tab?: \"about\"|\"contributors\"|\"models\"} — the About window: splash with community links, contributor and model credits (open: false closes it)",
     ),
-    ("window.toolsDoubleColumn", "Tools: Double Column", None, "{}"),
+    ("window.toolsDoubleColumn", "Tools: Double Column", None, "{on?: bool (default: toggle)} → whether the Tools panel has two columns"),
     (
         "window.workspace",
         "Workspace",
@@ -1829,7 +1829,10 @@ fn run_ui_inner(app: &mut DesignApp, id: &str, p: &Value) -> Option<Result<Value
             app.ui.pending_urls.push(url.clone());
             Ok(json!({"url": url}))
         }
-        "window.toolsDoubleColumn" => flag(&mut app.ui.tools_double_column),
+        "window.toolsDoubleColumn" => {
+            app.ui.tools_double_column = p.get("on").and_then(Value::as_bool).unwrap_or(!app.ui.tools_double_column);
+            Ok(json!(app.ui.tools_double_column))
+        }
         "window.collapseToIcons" => {
             app.ui.dock_expanded = false;
             app.ui.open_panel = None;