Class IntervalTicker

Ticker based on setInterval with a configurable interval. Optimized for Node.js and tests with fake timers.

Key features:

• Leading edge: callback is invoked via setTimeout(fn, 0) when interval > 0
• When interval === 0: setInterval(fn, 0) starts immediately (built-in leading-edge for 0)
• _timeoutId stores the setTimeout ID for leading-edge and is cleared in stop()
• active checks both timers: _timerId || _timeoutId