fix: 🐛 SynRadioGroup: SynRadio elements not clickable when they have no value while using form validation

[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: Any

Component

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

Environment

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

Description

When using an <syn-radio-group> with required set to true, it is not possible to select <syn-radio> elements that do not have a value property set when clicking on the item the first time.

This can be seen at https://codepen.io/schilchSICKAG/pen/JjgOxyv?editors=1000 in Shoelace. I also created a Shoelace Issue for this at shoelace-style/shoelace#2229.

Acceptance criteria

• All DoD items successfully completed
• <syn-radio> elements should be clickable when there is no value set and required is set to true.

[klaarseSICKAG]

please ping shoelace devs again

[klaarseSICKAG]

no stakeholder feedback yet. reopen if necessary