refactor(dialog): improve composition model and accessibility

Refactor Dialog 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**

- Simplify Dialog.Title / Dialog.Content / Dialog.Actions hierarchy
- Improve keyboard and accessibility handling
- Improve MD3 spacing and tonal elevation
- Reduce excessive wrappers

**Proposed API Direction**

``

**Performance Opportunities**

- Reduce nested layout complexity
- Improve portal interaction handling
- Reduce unnecessary rerenders during visibility updates

首先定位 Dialog 组件，并检查其当前基于 children 的组合方式、portal 行为和可见性更新。将现有公共 API 与提议的 title、content 和 actions props 进行比较，然后评估键盘、可访问性、MD3 间距、色调提升以及 wrapper 方面的更改。当在所述平台和边缘情况下都具备一致的 API 和一致的行为，并改善渲染特性时，即表示完成。

由索引模型根据 Issue 内容生成。