test(calculate): verify streak formulas for only weekend contribution… (JhaSourav07#1755)

…s timeline

## Description

Fixes JhaSourav07#1494

## Pillar

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

## Visual Preview

## 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

lib/calculate.test.ts

@@ -48,11 +48,15 @@ describe('calculateStreak', () => {
     ]);
 
     const result = calculateStreak(calendar);
-
     expect(result.currentStreak).toBe(0);
     expect(result.longestStreak).toBe(0);
     expect(result.totalContributions).toBe(0);
   });
+  it('verifies weekend only streaks', () => {
+    const c = buildCalendar([1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1]);
+    const s = calculateStreak(c);
+    expect(s.longestStreak).toBe(2);
+  });
 
   it('handles multiple weeks of zero contributions separating active streaks', () => {
     const calendar = buildCalendar([