[Fix] UI 0047403: HTML validator: Use role='group' for tree-containing slates

[fhelfer]

Problem: The UI Component documentation tool window triggered HTML validator errors: role="tree" and role="treeitem" are not allowed inside role="menu" (only menuitem, menuitemcheckbox, etc. are valid).

Solution:

• Add role="group" as an allowed ARIA role for Slates (valid container for tree content)
• Switch UI Component documentation from Tool to TreeTool so it uses the TreeToolItemRenderer
• TreeToolItemRenderer sets role="group" on its slate
• Main Bar Renderer no longer overwrites an existing ARIA role on slates

https://mantis.ilias.de/view.php?id=47403

[oliversamoila]

Hello @thibsy,
Could you please take this over directly, check it and, ideally, integrate it into Release 11 and Trunk. You will also need to decide whether Release 10 is applicable.

Best regards,
Oliver

[chfsx]

The changes in GS are fine, thanks!