refactor(card): modernize composition model and improve MD3 behavior

Refactor Card 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**

- Reduce dependence on deeply nested children
- Improve Card.Content / Card.Actions architecture
- Improve elevation and surface behavior
- Improve shape and outlined variants
- Simplify internal spacing rules

**Proposed API Direction**

Introduce clearer slot-based APIs:
`Content}
actions={[...]}
/>`

**Performance Opportunities**

- Reduce nested wrappers
- Optimize pressable behavior
- Avoid unnecessary subtree re-renders
- Improve memoization boundaries

该 issue 提到了 Card、Card.Content 和 Card.Actions，但没有指定文件或测试。首先定位 Card 的实现及其现有的公共 API，然后将当前的组合方式、变体、elevation、间距和 pressable 行为与提议的 slot 方向进行比较；完成标准和测试均未指定，因此需要与 maintainer 就范围达成一致。

由索引模型根据 Issue 内容生成。