test: Improve debounce/throttle test performance by replacing real timers with fake timers

[miinhho]

Summary

Replaced real timer usage with fake timers in debounce and throttle tests to eliminate flaky test risks and significantly improve test execution time.

Problem

• Tests were using real timers with delay() function, making them slow and potentially flaky
• Real timer-based tests are susceptible to timing issues in CI environments
• Total test execution time was unnecessarily long due to actual time delays

Solution

• Targeted approach: Only replaced real timers with fake timers for debounce and throttle tests that were the primary cause of slow test execution
• Simple replacements: For straightforward cases, replaced delay() calls with vi.advanceTimersByTime() for precise time control
• Preserved complex tests: When tests required additional modifications beyond simple delay() replacement, maintained original tests using vi.useRealTimers() to avoid breaking existing functionality

Performance Improvements

Individual Test Files

Test File	Before	After	Improvement
src/compat/function/debounce.spec.ts	4.08s	1.16s	3.52x faster
src/compat/function/throttle.spec.ts	5.08s	2.02s	2.52x faster
src/function/debounce.spec.ts	903ms	12ms	75.25x faster
src/function/throttle.spec.ts	1.45s	15ms	96.67x faster

Overall Test Suite Impact

Test execution time: 19.64s → 11.33s (42.3% improvement)

Benefits

• Eliminated flaky test risks - No dependency on system timing
• Faster CI/CD pipeline - Reduced test execution time by 42%
• More reliable tests - Deterministic timing behavior