test(utils): check boundary robustness of username length truncator (Variation 4) (JhaSourav07#1607)

## Description

Fixes JhaSourav07#1583

## Pillar

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

## Visual Preview
No visual changes (Pure layout safety unit test targeting username
truncation text length configurations).

## Checklist before requesting a review:

- [x] I have read the `CONTRIBUTING.md` file.
- [x] I have tested these changes locally.
- [x] My commits follow the Conventional Commits format (`test(utils):
...`).

Author: JhaSourav07

lib/svg/generator.test.ts

@@ -808,6 +808,20 @@ describe('generateSVG', () => {
       expect(svg).toContain('class="isometric-labels"');
       expect(svg).toContain('fill="var(--cp-text)"');
     });
+
+    it('verify boundary robustness of username length truncator (Variation 4)', () => {
+      const extendedLongUsername = 'abcdefghijklmnopqrstuvwxyz1234567890';
+      const extendedParams = {
+        user: extendedLongUsername,
+        hide_title: false,
+      } as unknown as BadgeParams;
+
+      const svg = generateSVG(mockStats, extendedParams, mockCalendar);
+
+      expect(extendedLongUsername.length).toBeGreaterThan(30);
+      expect(svg).toContain('ABCDEFGHIJKL...');
+      expect(svg).not.toContain('ABCDEFGHIJKLMNOPQRSTUVWXYZ');
+    });
   });
 });