• Feat: Add onFirstVisibleItemChanged so apps can track the item at the top of the viewport without setting up full viewability callbacks.
• Feat: Add experimental_adaptiveRender.initialMode for choosing whether adaptive rendering starts in normal or light mode before the list is ready.
• Perf: On Fabric, replacement container measurements are batched into the same layout pass, so scroll anchoring and item positioning recalculate once instead of once per pending row.