test(svg): verify truncateUsername caps long usernames in generateSVG (JhaSourav07#2223)

## Description

Fixes JhaSourav07#1082

## Pillar

- [x] 📐 Pillar 2 — Geometric SVG Improvement

## Visual Preview
This adds integration tests to assert username truncation behaviors.
Long usernames are verified to cap safely with trailing dots (`...`),
while short usernames are verified to contain no ellipsis.

## 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): ...`).
- [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

lib/svg/generator.test.ts

@@ -1564,6 +1564,41 @@ describe('Radar Scan Line Animation Alignment', () => {
     expect(geometryLong).toEqual(geometryBaseline);
   });
 
+  it('truncates usernames longer than 12 characters and adds an ellipsis in generateSVG', () => {
+    const longUsername = 'averylongusernamethatexceeds20chars'; // 36 characters
+    const expectedTruncated = 'AVERYLONGUSE...'; // 12 characters + '...' (in uppercase)
+
+    const svg = generateSVG(
+      mockStats,
+      { user: longUsername, size: 'medium', autoTheme: false } as unknown as BadgeParams,
+      mockCalendar
+    );
+
+    const titleMatch = svg.match(/<text[^>]*class="title"[^>]*>([^<]*)<\/text>/);
+    expect(titleMatch).not.toBeNull();
+    const renderedTitle = titleMatch?.[1];
+
+    expect(renderedTitle).toBe(expectedTruncated);
+    expect(renderedTitle).not.toContain(longUsername.toUpperCase());
+  });
+
+  it('does not truncate short usernames and leaves them without ellipsis in generateSVG', () => {
+    const shortUsername = 'abc'; // 3 characters
+
+    const svg = generateSVG(
+      mockStats,
+      { user: shortUsername, size: 'medium', autoTheme: false } as unknown as BadgeParams,
+      mockCalendar
+    );
+
+    const titleMatch = svg.match(/<text[^>]*class="title"[^>]*>([^<]*)<\/text>/);
+    expect(titleMatch).not.toBeNull();
+    const renderedTitle = titleMatch?.[1];
+
+    expect(renderedTitle).toBe(shortUsername.toUpperCase());
+    expect(renderedTitle).not.toContain('...');
+  });
+
   describe('glow parameter', () => {
     const mockStats: StreakStats = {
       currentStreak: 5,