v0.2.8

What's Changed

• fix: race-safe asyncSem — replaced bare channel variable with atomic.Pointer[chan struct{}] + sync.Once guard
• fix: atomic shouldNotify — converted customError.shouldNotify from bool to atomic.Bool to fix data race in concurrent NotifyAsync
• fix: safe type assertion in GetTraceId — comma-ok idiom prevents panic on non-string tracerID value
• Default async notification concurrency reduced from 1000 to 20
• Makefile bench regex fix (^$ → ^$$)