Signal form .reset() does not clear Angular Material error styling

### Which @angular/* package(s) are the source of the bug?

core, forms

### Is this a regression?

No

### Description

When using Angular Material form fields (`mat-form-field`) with signal-based forms (`@angular/forms/signals`), resetting the form after submission causes the Material input to display error styling (red outline) even though the field should no longer be in a touched or dirty state.

After calling `signalForm().reset()` on submit, the field value is correctly reset to an empty string. However, the Material form field renders as invalid with error styling applied. According to Angular Material's documented behavior, error styling should only be shown when the control has been touched. Since `reset()` is expected to clear both the `touched` and `dirty` states, the field should return to its pristine, untouched appearance — without any validation error indicators.

### Please provide a link to a minimal reproduction of the bug

https://stackblitz.com/github/mihai3636/2026--angular-signal-form-material-bug?file=src%2Fapp%2Fapp.ts

### Please provide the exception or error you saw

```true
N/A
```

### Please provide the environment you discovered this bug in (run `ng version`)

```true
Angular CLI : 22.0.4
Angular : 22.0.4
Node.js : 26.1.0
Package Manager : npm 11.13.0
Operating System : win32 x64

┌───────────────────────────┬───────────────────┬───────────────────┐
│ Package │ Installed Version │ Requested Version │
├───────────────────────────┼───────────────────┼───────────────────┤
│ @angular/build │ 22.0.4 │ ^22.0.0 │
│ @angular/cdk │ 22.0.2 │ ^22.0.2 │
│ @angular/cli │ 22.0.4 │ ^22.0.0 │
│ @angular/common │ 22.0.4 │ ^22.0.0 │
│ @angular/compiler │ 22.0.4 │ ^22.0.0 │
│ @angular/compiler-cli │ 22.0.4 │ ^22.0.0 │
│ @angular/core │ 22.0.4 │ ^22.0.0 │
│ @angular/forms │ 22.0.4 │ ^22.0.0 │
│ @angular/material │ 22.0.2 │ ^22.0.2 │
│ @angular/platform-browser │ 22.0.4 │ ^22.0.0 │
│ @angular/router │ 22.0.4 │ ^22.0.0 │
│ rxjs │ 7.8.2 │ ~7.8.0 │
│ typescript │ 6.0.3 │ ~6.0.2 │
│ vitest │ 4.1.9 │ ^4.0.8 │
└───────────────────────────┴───────────────────┴───────────────────┘
```

### Anything else?

_No response_

Beginne mit der verknüpften StackBlitz-Reproduktion und vergleiche signalForm().reset() mit dem Verhalten von @angular/forms/signals und Angular Material mat-form-field. Verfolge, wie reset den Status von touched, dirty und der Validierung aktualisiert; als abgeschlossen gilt die Aufgabe, wenn der Wert zurückgesetzt wird und das Material-Feld nach dem Absenden keine Fehlerdarstellung mehr anzeigt.

Vom Indexierungsmodell aus dem Issue-Text verfasst.