- Added marching_ants_offset to HcieIcedApp for animation state
- Added selection_bounds field to IcedDocument for persistent selection display
- Updated OverlayProgram to draw animated marching ants (black + white dashed lines)
- Added timer subscription for continuous animation when selection is active
- Updated SelectAll/Deselect handlers to properly manage selection state
- Selection now remains visible after creation with animated border
