bug(form-field): difficult to customize shape with tokens

### 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

19

### Description

When using mat-form-field in filled appearance, I want to shape the border-radius. I use this token
--mdc-filled-text-field-container-shape: 4px !important;
But it only applies to the top corners and not the bottom corners because this token uses the wrong container to set radius. It sets the radius on a level where the div for hints and errors is also included.
And by that the bottom corners are not set with that token

### Reproduction

StackBlitz link:
Steps to reproduce:
1.
2.

### Expected Behavior

Apply radius also to bottom corners

### Actual Behavior

not applying radius to bottom corners

### Environment

- Angular: 19
- CDK/Material: 19
- Browser(s): firefox
- Operating System (e.g. Windows, macOS, Ubuntu): windows

Comienza examinando la apariencia rellena de Angular Material mat-form-field y cómo se aplica --mdc-filled-text-field-container-shape. Reproduce el estilo indicado con Angular 19 y, después, rastrea qué contenedor es el propietario de las esquinas inferiores; se considera terminado cuando el token aplica de forma consistente el radio solicitado a todas las esquinas, incluso cuando hay textos de ayuda o errores.

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