pinnedViews + rapid state changes from stretchAmount every frame during overscroll
triggers SwiftUI memory corruption. ZStack overlay approach is crash-free:
- LazyVStack with no pinnedViews
- Inline tabs fade out when pinned threshold reached
- Overlay tabs (with safeAreaTop padding) fade in at top of ZStack
- Remove max(0) clamp in ScrollOffsetReader to allow negative values during bounce
- Add stretchAmount computed var (max(0, -scrollOffset))
- Hero image frame grows by stretchAmount and offsets upward on overscroll
- isCategoryTabsPinned still uses max(0, scrollOffset) via >= check
