fix(stepper): add disabled state to prevent navigation and provide visual feedback

src/app/shared/components/stepper/stepper.component.spec.ts

@@ -6,7 +6,7 @@ import { StepComponent } from './step.component';
 @Component({
   imports: [StepperComponent, StepComponent],
   template: `
-    <app-stepper #stepper>
+    <app-stepper #stepper [disabled]="stepperDisabled()">
       <app-step label="Step 1" [isValid]="step1Valid()">
         <div id="content-1">Content 1</div>
       </app-step>
@@ -20,6 +20,7 @@ class TestHostComponent {
   @ViewChild('stepper') stepper!: StepperComponent;
   step1Valid = signal(true);
   step2Valid = signal(true);
+  stepperDisabled = signal(false);
 }
 
 describe('StepperComponent & StepComponent', () => {
@@ -137,4 +138,28 @@ describe('StepperComponent & StepComponent', () => {
     expect(component.stepper.currentStepIndex()).toBe(0);
     expect(fixture.nativeElement.querySelector('#content-1')).not.toBeNull();
   });
+
+  it('blocks all navigation and shows visual feedback while disabled', async () => {
+    const { fixture, component } = await setup();
+    component.stepperDisabled.set(true);
+    fixture.detectChanges();
+
+    component.stepper.next();
+    expect(component.stepper.currentStepIndex()).toBe(0);
+
+    component.stepperDisabled.set(false);
+    fixture.detectChanges();
+    component.stepper.next();
+    expect(component.stepper.currentStepIndex()).toBe(1);
+
+    component.stepperDisabled.set(true);
+    fixture.detectChanges();
+    component.stepper.previous();
+    component.stepper.goToStep(0);
+
+    expect(component.stepper.currentStepIndex()).toBe(1);
+    const header = fixture.nativeElement.querySelector('.stepper-header');
+    expect(header.classList.contains('is-disabled')).toBe(true);
+    expect(header.getAttribute('aria-disabled')).toBe('true');
+  });
 });