Inventory click handling, TileView left click, test items
- Add onTileClick callback to TileView Ctor and constructor
- Move click handling from InvItemTile into TileView::mouseBtnDown
- TileView left click calculates grid index from mouse position
- Remove mouseBtnDown from InvItemTile
- Add InvUi::onInvClick handler (logs click index for now)
- Wire InvUi right panel to onInvClick via onTileClick callback
- Add temporary test Essence items to Player inventory
- Update acronyms doc: obsPtr and Ref entries