TextInput expands parent container unexpectedly

### Current behaviour
TextInput inside a flex container without width constraints, the input expands to full width, causing the parent container to stretch. Expected behavior is that it should respect the parent’s intrinsic size unless explicitly styled.

### Expected behaviour
Expand the parent container

未指定源文件或测试。首先在不受约束的 flex 容器中复现 TextInput，并比较当前的尺寸计算与预期的尺寸计算；在定位组件实现并为已达成共识的内在尺寸行为添加回归测试之前，先澄清关于预期行为的矛盾文本。

由索引模型根据 Issue 内容生成。