test(compareclient-type-compiler): add type validation coverage (JhaSourav07#3305)

## Description

Fixes JhaSourav07#2792 
## Summary

Added TypeScript compiler validation coverage for `CompareClient`
interfaces and schema structures.

## Changes Made

* Exported CompareClient interfaces for external type validation
* Added type compiler test coverage using `expectTypeOf`
* Verified:

  * `UserProfile` structure
  * `UserStats` optional fields
  * `LanguageData` schema
  * `ActivityData` optional properties
  * `CompareResponse` structure consistency

## Validation

```bash id="pl3k7m"
npx vitest ./app/compare/CompareClient.type-compiler.test.tsx
npm run lint
npm run format
```

## Pillar

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

## Visual Preview

## Checklist before requesting a review:

- [x] I have read the `CONTRIBUTING.md` file.
- [x] 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.
- [x] 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/compare/CompareClient.tsx

@@ -37,7 +37,7 @@ import {
 
 /* ── types ────────────────────────────────────────────────────────────── */
 
-interface UserProfile {
+export interface UserProfile {
   username: string;
   name: string;
   avatarUrl: string;
@@ -54,7 +54,7 @@ interface UserProfile {
   };
 }
 
-interface UserStats {
+export interface UserStats {
   currentStreak: number;
   peakStreak: number;
   totalContributions: number;
@@ -63,28 +63,28 @@ interface UserStats {
   totalIssues?: number;
 }
 
-interface LanguageData {
+export interface LanguageData {
   name: string;
   color: string;
   percentage: number;
 }
 
-interface ActivityData {
+export interface ActivityData {
   date: string;
   count: number;
   intensity: 0 | 1 | 2 | 3 | 4;
   locAdditions?: number;
   locDeletions?: number;
 }
 
-interface CompareUserData {
+export interface CompareUserData {
   profile: UserProfile;
   stats: UserStats;
   languages: LanguageData[];
   activity: ActivityData[];
 }
 
-interface CompareResponse {
+export interface CompareResponse {
   user1: CompareUserData;
   user2: CompareUserData;
   error?: string;

app/compare/CompareClient.type-compiler.test.tsx

@@ -0,0 +1,68 @@
+import { describe, expectTypeOf, it } from 'vitest';
+
+import type {
+  ActivityData,
+  CompareResponse,
+  CompareUserData,
+  LanguageData,
+  UserProfile,
+  UserStats,
+} from './CompareClient';
+
+describe('CompareClient Type Compiler Validation', () => {
+  it('validates UserProfile structure', () => {
+    expectTypeOf<UserProfile>().toEqualTypeOf<{
+      username: string;
+      name: string;
+      avatarUrl: string;
+      isPro: boolean;
+      bio: string;
+      location: string;
+      joinedDate: string;
+      developerScore: number;
+      stats: {
+        repositories: number;
+        followers: number;
+        following: number;
+        stars: number;
+      };
+    }>();
+  });
+
+  it('validates UserStats numeric and optional fields', () => {
+    expectTypeOf<UserStats>().toEqualTypeOf<{
+      currentStreak: number;
+      peakStreak: number;
+      totalContributions: number;
+      codingHabit?: string;
+      totalPRs?: number;
+      totalIssues?: number;
+    }>();
+  });
+
+  it('validates LanguageData structure', () => {
+    expectTypeOf<LanguageData>().toEqualTypeOf<{
+      name: string;
+      color: string;
+      percentage: number;
+    }>();
+  });
+
+  it('accepts optional fields in ActivityData without compile errors', () => {
+    expectTypeOf<ActivityData>().toEqualTypeOf<{
+      date: string;
+      count: number;
+      intensity: 0 | 1 | 2 | 3 | 4;
+      locAdditions?: number;
+      locDeletions?: number;
+    }>();
+  });
+
+  it('validates CompareResponse structure', () => {
+    expectTypeOf<CompareResponse>().toEqualTypeOf<{
+      user1: CompareUserData;
+      user2: CompareUserData;
+      error?: string;
+    }>();
+  });
+});