test(streak): verify unknown mode falls back to commits mode (JhaSourav07#2051)

## Description

Fixes JhaSourav07#1091

## Pillar
- [x] 🛠️ Other (Bug fix, refactoring, docs)

## Visual Preview
No visual changes — this is a test-only PR.

## Checklist before requesting a review:
- [x] I have read the `CONTRIBUTING.md` file.
- [x] I have tested these changes locally.
- [x] I have run `npm run format` and `npm run lint` locally and
resolved all errors.
- [x] My commits follow the Conventional Commits format.
- [x] I have made sure that i have only one commit to merge in this PR.
- [x] I have starred the repo.

Author: JhaSourav07

app/api/streak/route.test.ts

@@ -1361,6 +1361,14 @@ describe('GET /api/streak', () => {
     });
   });
 
+  it('falls back to commits mode when ?mode=unknown is given', async () => {
+    const response = await GET(makeRequest({ user: 'octocat', mode: 'invalid' }));
+
+    expect(response.status).toBe(200);
+    const body = await response.text();
+    expect(body).toContain('<svg');
+  });
+
   describe('org parameter validation', () => {
     it('returns 400 when org parameter is a User instead of an Organization', async () => {
       vi.mocked(getOrgDashboardData).mockRejectedValueOnce(