This implements SetPassCursor/GetPartsPassCursor HLL functions. The
pass_cursor flag controls whether the cursor "passes through" a
component to reach parts behind it.
Key changes to input processing:
- Iteration order changed from back-to-front to front-to-back for proper
cursor consumption
- MOUSE_ENTER / MOUSE_LEAVE now fire for all parts regardless of
clickable
- Click hit test uses clickable || !pass_cursor pre-filter
- pass_cursor=false parts consume the cursor, preventing hover and
click events from reaching parts behind them