[6.0] Fix default menu layout - submenu stay open on page load

[LadySolveig]

Pull Request for Issue #46364 .
Replacement for #46397 (same code that is tested, but moved to previous branch)

Summary of Changes

Introduce a new class (nav-active-open) for the default menu, allowing control over whether submenus are opened automatically on page load for the active menu item.

Caution

This functionality should not be activated by default without an additional class for all default menus, as it may not be desirable in various other module positions.
Example - Cassiopeia menu position

Additionally updated the toggleSubMenu method to use optional chaining when setting the aria-expanded attribute, preventing errors if the target element is missing.

Testing Instructions

• Install Blog-Sample-Data
• Move the Main Menu Blog module to position sidebar-right
• Switch the layout to Default

Step 1

• Open site in frontend and select submenu entry Help -> Workflows

Step 2

• Edit Main Menu Blog module - add class nav-active-open
• Open site in frontend and select submenu entry Help -> Workflows

Important

For this to test an update of the media asset is required, please use the prebuilt packages or run npm install.

menu-fix.mp4

Actual result BEFORE applying this Pull Request

Should always be collapsed - with and without the class.

Expected result AFTER applying this Pull Request

Step 1
Submenu with menu entry Workflows should be always collapsed (without the class).
Step 2
Submenu with menu entry Workflows should stay open on new page load if Workflow is the current active item (with class set).

Link to documentations

Please select:

• Documentation link for docs.joomla.org:

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed

[Bodge-IT]

Code not technically changed from previous tested code

[softforge]

Thank you @LadySolveig and the testers from the previous PR