Menu popup: visibility, zoom sync, and tab fixes

Track menu popup visibility and propagate zoom level to the popup. Add menu_popup_visible_ flag, SendMenuPopupZoom(), and call it when creating/showing the popup and when adjusting zoom. Make CreateNewTab accept an optional URL and route popup/new-tab flows to it. Prevent per-tab child closes from triggering app shutdown by tracking closing_tab_browsers_ and adding ForgetClosingTabBrowser(). Treat MenuPopup role specially when enabling frame hit-testing.

Platform: remove usage of ApplyRoundedBrowserRegion and switch menu popup sizing to use resized client_size helpers (consolidate calculations across Win/Mac/Linux). UI: update menu-popup CSS/JS (new styling, font, zoom formatting API via NebulaMenuPopup.setZoomLevel), wire settings to use nebulaNative.postMessage for new-tab, and remove the static menu-popup.html. Misc: small chrome CSS/JS tweaks and ensure chrome state includes zoomLevel.

src/cef/browser_client.cpp

@@ -51,8 +51,8 @@ bool NebulaBrowserClient::OnProcessMessageReceived(CefRefPtr<CefBrowser> browser
         return false;
     }
 
-    if (role_ != BrowserRole::Chrome && role_ != BrowserRole::MenuPopup &&
-        role_ != BrowserRole::Content) {
+    if (role_ != BrowserRole::Chrome && role_ != BrowserRole::Content &&
+        role_ != BrowserRole::MenuPopup) {
         return false;
     }
 
@@ -64,6 +64,7 @@ bool NebulaBrowserClient::OnProcessMessageReceived(CefRefPtr<CefBrowser> browser
             command == "navigate-insecure" && IsInsecureInterstitialFrame(frame);
         const bool allowed_settings_command =
             IsSettingsFrame(frame) && (command == "navigate" ||
+                                       command == "new-tab" ||
                                        command == "clear-site-history" ||
                                        command == "clear-search-history");
         if (!allowed_insecure_command && !allowed_settings_command) {