🎨 Palette: Add proper label association to In-Game Name input

[google-labs-jules]

💡 What:
Added proper label association for the "In-Game Name" text input in activity/src/components/RoleEditor.tsx. Replaced the generic <div> with a semantic <label> tag and linked it to the input field using a unique ID generated via React's useId() hook.

🎯 Why:
Previously, the "In-Game Name" label was just a text string inside a <div>, which means screen readers could not programmatically associate it with the text input field. Linking them improves accessibility compliance and allows users to click the label to focus the input.

📸 Before/After:
No visual changes.

♿ Accessibility:

• Converted div.role-editor-label to a semantic <label> tag.
• Added id to the text input and an htmlFor attribute to the label, linking the two.

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PR created automatically by Jules for task 15328447738242946101 started by @TytaniumDev

[google-labs-jules]

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