bug(COMPONENT): MatDatePicker

### Is this a regression?

- [ ] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

_No response_

### Description

MatDatePicker with Signal Forms keeps on showin matDatepickerParse error if delete with keyboard a valid date un char at the time.

### Reproduction

StackBlitz link:
Steps to reproduce:
1.
2.

### Expected Behavior

Bind the control to a value.
Select or enter a valid date.
Erase the just entered date.
The forms has invalid()==false

### Actual Behavior

Bind the control to a value.
Select or enter a valid date.
Erase the just entered date.
The forms has invalid()==true

### Environment

- Angular: 22
- CDK/Material: 22
- Browser(s):
- Operating System (e.g. Windows, macOS, Ubuntu):

未提供源文件、测试或复现链接。首先使用 Angular Signal Forms 复现 MatDatePicker 的行为：绑定一个 control，输入一个有效日期，然后逐个字符擦除。完成标准是：清除日期后，表单的无效状态为 false，且没有 matDatepickerParse 错误。

由索引模型根据 Issue 内容生成。