test: add benchmark-svg test coverage (JhaSourav07#2383)

## Description
Adds a focused unit test file for scripts/benchmark-svg.ts with 5
targeted checks:
- benchmark header logging
- warmup + timed run invocation counts
- theme block logging coverage
- floating-point timing formatting to 2 decimals
- separator output per theme

Fixes JhaSourav07#2361

## Pillar
Testing reliability

## Checklist
- [x] I read the contributing guide
- [x] I kept the change small and focused
- [x] I added focused tests

## Testing
- Local itest run was blocked in this environment due disk space
(ENOSPC) while resolving test runner dependencies.
- CI should run the full checks on PR.

Author: JhaSourav07

scripts/benchmark-svg.test.ts

@@ -0,0 +1,114 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+const perfHooksMock = vi.hoisted(() => ({
+  performance: {
+    now: vi.fn(),
+  },
+}));
+
+vi.mock('../lib/svg/generator', () => ({
+  generateSVG: vi.fn(() => '<svg/>'),
+}));
+
+vi.mock('../lib/svg/sanitizer', () => ({
+  hexColor: vi.fn((value: string) => `#${value}`),
+  sanitizeSpeed: vi.fn(() => '8s'),
+}));
+
+vi.mock('perf_hooks', () => ({
+  ...perfHooksMock,
+  default: perfHooksMock,
+}));
+
+async function runBenchmarkScript() {
+  vi.resetModules();
+  await import('./benchmark-svg');
+}
+
+describe('scripts/benchmark-svg', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('prints the benchmark header', async () => {
+    const logSpy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    const { performance } = await import('perf_hooks');
+    vi.mocked(performance.now).mockImplementation(() => 1);
+
+    await runBenchmarkScript();
+
+    expect(logSpy).toHaveBeenCalledWith('\nSVG Benchmark Results\n');
+  });
+
+  it('runs warmup plus 20 timed iterations for each theme', async () => {
+    const logSpy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    const { performance } = await import('perf_hooks');
+    const { generateSVG } = await import('../lib/svg/generator');
+
+    let tick = 0;
+    vi.mocked(performance.now).mockImplementation(() => {
+      tick += 1;
+      return tick;
+    });
+
+    await runBenchmarkScript();
+
+    expect(generateSVG).toHaveBeenCalledTimes(63);
+    expect(vi.mocked(generateSVG).mock.calls[0]?.[1]).toMatchObject({
+      bg: '#0d1117',
+      accent: '#00ffaa',
+      text: '#ffffff',
+    });
+    expect(logSpy).toHaveBeenCalled();
+  });
+
+  it('logs all theme names', async () => {
+    const logSpy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    const { performance } = await import('perf_hooks');
+    vi.mocked(performance.now).mockImplementation(() => 1);
+
+    await runBenchmarkScript();
+
+    expect(logSpy).toHaveBeenCalledWith('Theme: dark');
+    expect(logSpy).toHaveBeenCalledWith('Theme: light');
+    expect(logSpy).toHaveBeenCalledWith('Theme: purple');
+  });
+
+  it('formats floating-point benchmark numbers to 2 decimals', async () => {
+    const logSpy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    const { performance } = await import('perf_hooks');
+
+    let call = 0;
+    vi.mocked(performance.now).mockImplementation(() => {
+      call += 1;
+      if (call % 2 === 1) return call;
+      return call + 1.2345;
+    });
+
+    await runBenchmarkScript();
+
+    const lines = logSpy.mock.calls
+      .map((args) => String(args[0]))
+      .filter(
+        (line) => line.startsWith('Average:') || line.startsWith('Min:') || line.startsWith('Max:')
+      );
+
+    expect(lines.length).toBe(9);
+    for (const line of lines) {
+      expect(line).toMatch(/:\s\d+\.\d{2}ms$/);
+    }
+  });
+
+  it('prints separator line after each theme block', async () => {
+    const logSpy = vi.spyOn(console, 'log').mockImplementation(() => {});
+    const { performance } = await import('perf_hooks');
+    vi.mocked(performance.now).mockImplementation(() => 1);
+
+    await runBenchmarkScript();
+
+    const separatorCalls = logSpy.mock.calls.filter(
+      (args) => args[0] === '--------------------------'
+    );
+    expect(separatorCalls).toHaveLength(3);
+  });
+});