Sidebar table list scrolls laggily / stutters when dragging #24

The tables list in the left sidebar lags behind the scrollbar thumb and stutters while dragging, especially with many tables.

Cause

• The scroll container is not promoted to a compositing layer, so it runs on the 60Hz timer path instead of the display's native rate (120Hz on ProMotion) that the rest of the UI uses.
• The virtual-window state was updated inside requestAnimationFrame, leaving the rendered rows one frame behind the scrollbar.
• The fixed row stride (ROW_H) slightly overestimated the real row height, causing drift.

Expected
Smooth, native-rate scrolling that keeps up with the pointer.

Addressed by #20.