V8 Coverage showing unexpected results

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

Don't known / other

### Is this a regression?

No

### Description

I'm in the process of migrating from jasmine/karma with istanbul coverage to vitest with v8 coverage. I'm currently migrating around 2500 unit tests. With Istanbul I had over 95% coverage across statements, branches, functions and lines. With vitest I'm seeing lower coverage, mainly on the branches with 90%.

I've noticed that even empty classes (template only) show 90% branch coverage (9/10).

A minimal reproduction:
* Create a new Angular 21 application: `ng new ng21`
* Install v8 coverage `npm i --save-dev @vitest/coverage-v8`
* Remove the protected title variable from app.ts `-- protected readonly title = signal('ng21');`
* Remove the `should render title` test from app.spec.ts
* Run `ng test --coverage`

This is the coverage I see:

Similar from my project:

with the spec file as:
```
import { TestBed } from '@angular/core/testing';
import { HeaderComponent } from './header.component';
import { HeaderComponent as ClsHeaderComponent, TenantDropdownComponent } from '@cls/ui-util';
import { MockComponent } from '@cls/ui-util/testing';
import { SearchComponent } from '../../schedule/components/search/search.component';

describe('HeaderComponent', () => {
beforeEach(async () => {
await TestBed.configureTestingModule({
imports: [HeaderComponent],
providers: []
})
.overrideComponent(HeaderComponent, {
remove: { imports: [SearchComponent, ClsHeaderComponent, TenantDropdownComponent] },
add: {
imports: [
MockComponent({ selector: 'app-search' }) as any,
MockComponent({ selector: 'cls-header' }) as any,
MockComponent({ selector: 'cls-tenant-dropdown' }) as any
]
}
})
.compileComponents();
});

function setup() {
const fixture = TestBed.createComponent(HeaderComponent);

return {
fixture,
app: fixture.componentInstance,
compiled: fixture.debugElement.nativeElement
};
}

it('should create the app', () => {
const { app } = setup();
expect(app).toBeTruthy();
});
});
```

angular.json
```
"test": {
"builder": "@angular/build:unit-test",
"options": {
"browsers": ["chromium"],
"buildTarget": "admin-ui:build",
"headless": true,
"tsConfig": "./tsconfig.spec.json",
"runnerConfig": "./vitest.config.ts",
"coverage": true,
"coverageInclude": ["src/app/**/*.ts"],
"coverageExclude": ["index.ts", "main.ts", "polyfills.ts", "**/*.routes.ts", "**/*.model.ts", "**/*.interface.ts"],
"coverageReporters": ["text", "html", "lcov"],
"coverageThresholds": {
"statements": 90,
"branches": 90,
"functions": 90,
"lines": 90
}
}
}
```

vitest.config.ts
```
import { defineConfig } from 'vitest/config';

export default defineConfig({
test: {
environment: 'jsdom',
globals: true,
setupFiles: ['src/test-setup.ts'],
restoreMocks: true,
coverage: {
provider: 'v8'
},
browser: {
screenshotFailures: false
}
}
});
```

Have I misconfigured something? Do I have an incorrect assumption of v8 coverage or is there an issue here?

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

_No response_

### Please provide the exception or error you saw

```true

```

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

```true
Angular CLI : 21.2.3
Angular : 21.2.5
Node.js : 22.13.1
Package Manager : npm 10.9.2
Operating System : darwin arm64

┌───────────────────────────────────┬───────────────────┬───────────────────┐
│ Package │ Installed Version │ Requested Version │
├───────────────────────────────────┼───────────────────┼───────────────────┤
│ @angular/animations │ 21.2.5 │ ~21.2.0 │
│ @angular/build │ 21.2.3 │ ^21.2.0 │
│ @angular/cdk │ 21.2.3 │ ~21.2.0 │
│ @angular/cli │ 21.2.3 │ ~21.2.0 │
│ @angular/common │ 21.2.5 │ ~21.2.0 │
│ @angular/compiler │ 21.2.5 │ ~21.2.0 │
│ @angular/compiler-cli │ 21.2.5 │ ~21.2.0 │
│ @angular/core │ 21.2.5 │ ~21.2.0 │
│ @angular/forms │ 21.2.5 │ ~21.2.0 │
│ @angular/language-service │ 21.2.5 │ ~21.2.0 │
│ @angular/platform-browser │ 21.2.5 │ ~21.2.0 │
│ @angular/platform-browser-dynamic │ 21.2.5 │ ~21.2.0 │
│ @angular/router │ 21.2.5 │ ~21.2.0 │
│ rxjs │ 7.8.2 │ ~7.8.2 │
│ typescript │ 5.9.3 │ ~5.9.3 │
│ vitest │ 4.1.0 │ ^4.0.18 │
│ zone.js │ 0.15.1 │ ~0.15.0 │
└───────────────────────────────────┴───────────────────┴──────────────────
```

### Anything else?

_No response_

Start with the Angular 21 reproduction using `ng test --coverage`, then inspect `angular.json` and `vitest.config.ts` alongside the changes to `app.ts` and `app.spec.ts`. Compare the V8 branch report for the empty component with the configured coverage includes and excludes. Done means establishing whether the result is expected V8 behavior or an Angular CLI unit-test builder defect, with a reproducible case and expected coverage behavior documented.

Written by the indexing model from the issue text.