feat: scaffold useDragManager hook with types and state

packages/web/src/hooks/useDragManager.ts

@@ -0,0 +1,54 @@
+import { useState, useCallback, useEffect, type RefObject } from 'react';
+
+export type DragType = 'channel' | 'category' | 'voiceUser';
+
+export interface DragState {
+  type: DragType;
+  dragId: string;
+  sourceId?: string; // only for voiceUser — originating channelId
+}
+
+export interface DropTarget {
+  targetId: string;
+  position: 'before' | 'after';
+  targetType: 'channel' | 'category';
+}
+
+interface UseDragManagerOpts {
+  scrollContainerRef: RefObject<HTMLElement | null>;
+  canManage: boolean;
+  canMoveMembers: boolean;
+  onChannelDrop: (dragId: string, target: DropTarget) => void;
+  onCategoryDrop: (dragId: string, target: DropTarget) => void;
+  onVoiceUserDrop: (userId: string, fromChannelId: string, toChannelId: string) => void;
+}
+
+export function useDragManager(opts: UseDragManagerOpts) {
+  const { scrollContainerRef, canManage, canMoveMembers, onChannelDrop, onCategoryDrop, onVoiceUserDrop } = opts;
+
+  const [activeDrag, setActiveDrag] = useState<DragState | null>(null);
+  const [dropTarget, setDropTarget] = useState<DropTarget | null>(null);
+  const [voiceHoverChannelId, setVoiceHoverChannelId] = useState<string | null>(null);
+
+  const clearState = useCallback(() => {
+    setActiveDrag(null);
+    setDropTarget(null);
+    setVoiceHoverChannelId(null);
+  }, []);
+
+  // Handler factories added in subsequent stages...
+
+  // Suppress unused variable warnings for incremental build
+  void scrollContainerRef;
+  void canManage;
+  void canMoveMembers;
+  void onChannelDrop;
+  void onCategoryDrop;
+  void onVoiceUserDrop;
+  void clearState;
+
+  return {
+    activeDrag,
+    dropTarget,
+  };
+}