fix: 🐛 SynTabGroup does not allow nested SynTabGroup as a child

[schilchSICKAG]

Checklist (for the issue creator)

• I have verified the bug exists in the latest version of @synergy-design-system/components (e.g. via pnpm install @synergy-design-system/components).
• I can provide a simple, reproducible example of the issue (e.g. via code-sandbox or sample code, ...).
• I would be willing to provide a PR for this issue.

Version

The bug occurred with the following version of the component library: 2.18.0

Component

The issue arises when using the following component(s): syn-tab-group, syn-tab-panel

Environment

The issue occurred with the following operating system(s): All
The issue occurred in the following browser(s): All

Description

As a developer I want to have the possibility to use a <syn-tab-group> that is nested into another <syn-tab-group>. This may come in handy for structuring applications with both left and top navigations, for example. When nesting tab groups and selecting one of the children tabs, the whole tab group content disappears as the child tries to control the parent and the given tab cannot be found in its associated elements. An example of this can be seen at https://codepen.io/schilchSICKAG/pen/NPKeVgj?editors=1110

Acceptance criteria

• All DoD items successfully completed
• Nesting tab groups into other tab-groups does not lead to errors.
• Create a shoelace ticket

[schilchSICKAG]

This seems to be a regression in Shoelace 2.19.1, see shoelace-style/shoelace#2320.

Will provide a fix for Shoelace when tackling this

[schilchSICKAG]

Shoelace PR available at shoelace-style/shoelace#2367