refactor(studio): drop the duplicate inspector-open computation

The rebase onto main left two identical inspectorButtonActive/inspectorOpen
constants after a conflict resolution; only the first was still referenced.

Author: miguel-heygen

packages/studio/src/components/StudioHeader.tsx

@@ -175,7 +175,6 @@ export function StudioHeader({
 }: StudioHeaderProps) {
   const { projectId, editHistory, handleUndo, handleRedo, renderQueue } = useStudioShellContext();
   const { rightCollapsed, setRightCollapsed, setRightPanelTab } = usePanelLayoutContext();
-  const inspectorOpen = !rightCollapsed && inspectorPanelActive;
   const isRendering = renderQueue.isRendering;
   const ffmpegMissing = renderQueue.ffmpegMissing;
   // The dock has no separate "railed by window width" state (it shrinks