Improves header drawer rendering to support multi-row event stacking
Adds row-based layout algorithm for all-day events
Enables flexible height expansion based on event count
Provides more robust event placement across visible date range
Updates header and viewport components to use CSS subgrid for more flexible layout
Improves grid structure by:
- Replacing fixed grid columns with subgrid
- Adjusting scrollbar and overflow properties
- Simplifying header and track element positioning
Updates ScrollManager to dynamically sync header spacer height using ResizeObserver
Removes explicit spacer animation from HeaderDrawerManager
Simplifies header and scroll interaction by moving height synchronization logic to ScrollManager
