phsl / new-api

Standardize the scrollbar appearance of semi-sidesheet-body to match the existing semi-table-body style. This change:
- Sets scrollbar width to 6px
- Applies light gray color (rgba(var(--semi-grey-2), 0.3))
- Adds subtle hover effect
- Uses 2px border radius for consistency
- Improves overall UI cohesion across components