speaking! (#5925)

frontend/src/core/constants/zIndex.ts

@@ -0,0 +1,25 @@
+/**
+ * Z-index constants for layering elements across the application
+ * Organized in ascending order to prevent conflicts
+ */
+
+export const ZINDEX = {
+  // Base layers
+  BASE: 0,
+
+  // Overlay/modal layers
+  MODAL_BACKDROP: 1000,
+  MODAL_CONTENT: 1001,
+
+  // Popover/tooltip layers
+  POPOVER: 1100,
+  TOOLTIP: 1200,
+
+  // Viewer specific layers
+  VIEWER_HIGHLIGHT: 999,
+  VIEWER_ANNOTATION_MENU: 1300,
+
+  // Sticky/fixed layers
+  STICKY_HEADER: 900,
+  STICKY_SIDEBAR: 850,
+} as const;