Transmission #050: Inventory layout — equipment inside Items tab

Reworked InventoryPanelUI so the modal uses one wide panel (panelWidth + gap + equipmentWidth) centered on screen, with equipment docked inside that panel on the right (same vertical band as the grid) instead of a separate canvas sibling that sat on top of tabs. Skills, Stats, Grimoire, and other progression tabs now use the full inner width for their scroll areas. Equipment, the tooltip strip, and Use / Equip / Unequip / Split only show when the Items tab is active and the panel is expanded, so they no longer steal clicks from other tabs.