refactor(radio-button): modernize selection model and improve MD3 compliance

[ruben-rebelo]

Refactor RadioButton to improve Material Design 3 compliance, remove problematic children patterns, improve performance characteristics, and modernize the public API.

Problems

• Current API relies heavily on children composition in ways that are difficult to optimize
• Internal layout logic is tightly coupled to arbitrary child structures
• MD3 behaviors and visuals are not fully aligned with current Material guidelines
• Rendering performance can degrade in large lists or frequently updated screens
• Type safety and discoverability of the API can be improved
• The component has inconsistent behavior between platforms and edge cases

Focus Areas

• Improve RadioButton.Group architecture
• Improve accessibility semantics
• Improve spacing and density consistency
• Simplify internal selection propagation

Proposed API Direction

<RadioButton.Group value={value} onValueChange={setValue} />

Performance Opportunities

• Reduce context-driven rerenders
• Improve group memoization
• Simplify animation paths