refactor: restructure files to their domains, new preview overlay system, and dep graph

apps/web/src/timeline/components/drag-line.tsx

@@ -0,0 +1,29 @@
+import { getDropLineY } from "./drop-target";
+import type { TimelineTrack, DropTarget } from "@/timeline";
+import { TIMELINE_LAYERS } from "./layers";
+
+interface DragLineProps {
+	dropTarget: DropTarget | null;
+	tracks: TimelineTrack[];
+	isVisible: boolean;
+	headerHeight?: number;
+}
+
+export function DragLine({
+	dropTarget,
+	tracks,
+	isVisible,
+	headerHeight = 0,
+}: DragLineProps) {
+	if (!isVisible || !dropTarget) return null;
+
+	const y = getDropLineY({ dropTarget, tracks });
+	const lineTop = y + headerHeight;
+
+	return (
+		<div
+			className="bg-primary pointer-events-none absolute right-0 left-0 h-0.5"
+			style={{ top: `${lineTop}px`, zIndex: TIMELINE_LAYERS.dragLine }}
+		/>
+	);
+}