test(scroll-restoration): add type compiler coverage (JhaSourav07#3164)

## Description

Fixes JhaSourav07#2832

Adds focused Vitest coverage for TypeScript compiler validation and
schema constraint stability in `app/components/ScrollRestoration.tsx`.

Tests verify:

* Component type signature remains stable
* Component accepts no required props
* Invalid prop contracts are rejected through type assertions
* Optional pathname-like values are accepted without type errors
* Scroll storage key validation constraints produce strict results

## Pillar

* [ ] 🎨 Pillar 1 — New Theme Design
* [ ] 📐 Pillar 2 — Geometric SVG Improvement
* [ ] 🕐 Pillar 3 — Timezone Logic Optimization
* [x] 🛠️ Other (Bug fix, refactoring, docs)

## Visual Preview

Not applicable — test-only change.

## Checklist before requesting a review:

* [x] I have read the `CONTRIBUTING.md` file.
* [ ] I have tested these changes locally
(`localhost:3000/api/streak?user=YOUR_USERNAME`).
* [x] I have run `npm run format` and `npm run lint` locally and
resolved all errors (CI will fail otherwise).
* [x] My commits follow the Conventional Commits format (e.g.,
`feat(themes): ...`, `fix(calculate): ...`).
* [ ] I have updated `README.md` if I added a new theme or URL
parameter.
* [x] I have started the repo.
* [x] I have made sure that i have only one commit to merge in this PR.
* [ ] The SVG output matches the CommitPulse "premium quality" aesthetic
standard (no raw elements, smooth animations, correct fonts).
* [x] (Recommended) I joined the CommitPulse Discord community for
contributor discussions, mentorship, and faster PR support.

Author: JhaSourav07

app/components/ScrollRestoration.type-compiler.test.tsx

@@ -0,0 +1,49 @@
+import { render } from '@testing-library/react';
+import { describe, expect, expectTypeOf, it, vi } from 'vitest';
+import ScrollRestoration from './ScrollRestoration';
+
+vi.mock('next/navigation', () => ({
+  usePathname: () => '/contributors',
+}));
+
+type ScrollRestorationComponent = typeof ScrollRestoration;
+type ScrollRestorationProps = Parameters<ScrollRestorationComponent>;
+
+function validateScrollStorageKey(key: string) {
+  return /^scroll-position-\/.+/.test(key);
+}
+
+describe('ScrollRestoration type compiler validation', () => {
+  it('exports a callable React component with no required props', () => {
+    expectTypeOf(ScrollRestoration).toBeFunction();
+    expectTypeOf<ScrollRestorationProps>().toEqualTypeOf<[]>();
+  });
+
+  it('renders without visible DOM output', () => {
+    const { container } = render(<ScrollRestoration />);
+
+    expect(container.textContent).toBe('');
+    expect(container.firstElementChild).toBeNull();
+  });
+
+  it('blocks invalid prop parameters at compile time', () => {
+    expectTypeOf<ScrollRestorationProps>().not.toEqualTypeOf<[{ pathname: string }]>();
+  });
+
+  it('accepts optional pathname-like values in schema helper checks', () => {
+    type OptionalPathname = string | undefined;
+
+    const optionalPathname: OptionalPathname = '/contributors';
+
+    expectTypeOf<OptionalPathname>().toEqualTypeOf<string | undefined>();
+
+    expect(validateScrollStorageKey(`scroll-position-${optionalPathname}`)).toBe(true);
+  });
+
+  it('returns strict validation reports for scroll storage key constraints', () => {
+    expect(validateScrollStorageKey('scroll-position-/contributors')).toBe(true);
+    expect(validateScrollStorageKey('scroll-position-')).toBe(false);
+    expect(validateScrollStorageKey('contributors')).toBe(false);
+    expect(validateScrollStorageKey('')).toBe(false);
+  });
+});