Summary

Add smooth auto-scroll behavior when selecting layers, both in the layer
tree panel and on the canvas/iframe viewport.

Changes

• Replace row-level scrollIntoView with virtualizer-based two-step scroll (instant jump + smooth centering) in LayersTree
• Skip scrolling when the selected layer is already visible within a 64px margin
• Add canvas auto-scroll to the selected element with zoom-aware position calculation
• Handle initial page load with retry mechanism for elements not yet in the DOM
• Re-scroll on content height changes during the first 5s to correct image loading layout shifts
• Clean up unused scrollToSelected prop and rowRef from LayerRow
• Fix Tailwind lint warning and missing useMemo dependency

Test plan

• Click an element on the canvas — layer tree should smoothly scrolls to it if it was not visible
• Click a layer in the layer tree — canvas should smoothly scrolls to the element
• Select a layer already visible in both panels — no unnecessary scroll
• Reload the builder with a pre-selected layer deep in the page — both panels scroll to it on load
• Test with a page containing many images — scroll position corrects after images load
• Test at different zoom levels — canvas scroll lands on the correct element