Fix full Shadow DOM rebuild on every render

[thedhanawada]

Problem

BaseComponent.render() nukes the entire Shadow DOM tree and rebuilds from scratch on every state change. This causes:

• Layout thrashing / flicker
• Loss of focus state
• Loss of scroll position
• Poor performance with many events

Fix

Implement incremental/differential rendering. Only update the parts of the DOM that actually changed. Consider a simple virtual DOM diff or targeted DOM patches.