fix: support dropping file tree nodes to root blank area

web/app/components/workflow/skill/file-tree/tree/file-tree.spec.tsx

@@ -37,6 +37,11 @@ type MockInlineCreateNodeResult = {
 
 type MockTreeApi = {
   deselectAll: () => void
+  dragNode?: {
+    id: string
+    parent: { id: string, isRoot?: boolean } | null
+  } | null
+  get: (id: string | null) => { id: string, children?: Array<{ id: string }> } | undefined
   state: {
     nodes: {
       drag: {
@@ -89,6 +94,12 @@ function createNode(overrides: Partial<AppAssetTreeView> = {}): AppAssetTreeView
 function createTreeApiMock(): MockTreeApi {
   return {
     deselectAll: vi.fn(),
+    dragNode: null,
+    get: vi.fn((id: string | null) => {
+      if (id === 'root')
+        return undefined
+      return id ? { id, children: [] } : undefined
+    }),
     state: {
       nodes: {
         drag: {
@@ -440,6 +451,25 @@ describe('FileTree', () => {
       expect(mocks.rootDropHandlers.handleRootDragLeave).toHaveBeenCalledTimes(1)
       expect(mocks.rootDropHandlers.handleRootDrop).toHaveBeenCalledTimes(1)
     })
+
+    it('should commit internal move when dropping in root blank area', () => {
+      mocks.treeApi.dragDestinationIndex = 2
+      mocks.treeApi.dragNode = {
+        id: 'file-1',
+        parent: { id: 'folder-1', isRoot: false },
+      }
+      mocks.treeApi.state.nodes.drag = {
+        id: 'file-1',
+        destinationParentId: 'root',
+        destinationIndex: 2,
+      }
+
+      render(<FileTree />)
+
+      fireEvent.drop(getTreeDropZone())
+
+      expect(mocks.executeMoveNode).toHaveBeenCalledWith('file-1', null)
+    })
   })
 
   describe('Tree callbacks', () => {

web/app/components/workflow/skill/file-tree/tree/file-tree.tsx

@@ -41,6 +41,13 @@ type DragInsertTarget = {
   parentId: string | null
   index: number
 }
+type CommitInternalMoveArgs = {
+  nodeId: string
+  draggedNode: NodeApi<TreeNodeData>
+  parentId: string | null
+  index: number
+  parentNode?: NodeApi<TreeNodeData> | null
+}
 
 const normalizeParentId = (node: NodeApi<TreeNodeData> | null | undefined) => {
   if (!node || node.isRoot)
@@ -185,6 +192,35 @@ const FileTree = ({ className }: FileTreeProps) => {
   const { executeMoveNode } = useNodeMove()
   const { executeReorderNode } = useNodeReorder()
 
+  const commitInternalMove = useCallback(({
+    nodeId,
+    draggedNode,
+    parentId,
+    index,
+    parentNode,
+  }: CommitInternalMoveArgs) => {
+    const tree = treeRef.current
+    const destinationIndex = tree?.dragDestinationIndex
+    const isInsertLine = destinationIndex !== null && destinationIndex !== undefined
+    const targetParentId = parentId ?? null
+    const sourceParentId = normalizeParentId(draggedNode.parent)
+
+    if (isInsertLine && sourceParentId === targetParentId) {
+      const siblingIds = getSiblingIds(parentNode, tree)
+      const afterNodeId = getAfterNodeIdForReorder(
+        siblingIds,
+        nodeId,
+        destinationIndex ?? index,
+      )
+      if (afterNodeId !== undefined) {
+        executeReorderNode(nodeId, afterNodeId)
+        return
+      }
+    }
+
+    executeMoveNode(nodeId, targetParentId)
+  }, [executeMoveNode, executeReorderNode])
+
   const syncDragInsertTarget = useCallback(() => {
     const tree = treeRef.current
     if (!tree)
@@ -231,28 +267,43 @@ const FileTree = ({ className }: FileTreeProps) => {
     if (!nodeId || !draggedNode)
       return
 
+    commitInternalMove({
+      nodeId,
+      draggedNode,
+      parentId,
+      index,
+      parentNode,
+    })
+  }, [commitInternalMove])
+
+  const handleTreeDrop = useCallback((e: React.DragEvent<HTMLDivElement>) => {
+    handleRootDrop(e)
+
     const tree = treeRef.current
-    const destinationIndex = tree?.dragDestinationIndex
-    const isInsertLine = destinationIndex !== null && destinationIndex !== undefined
-    const targetParentId = parentId ?? null
-    const sourceParentId = normalizeParentId(draggedNode.parent)
+    const dragTarget = dragInsertTargetRef.current
+    if (!tree || !dragTarget)
+      return
 
-    if (isInsertLine && sourceParentId === targetParentId) {
-      const siblingIds = getSiblingIds(parentNode, tree)
-      const afterNodeId = getAfterNodeIdForReorder(
-        siblingIds,
-        nodeId,
-        destinationIndex ?? index,
-      )
-      if (afterNodeId !== undefined) {
-        executeReorderNode(nodeId, afterNodeId)
-        return
-      }
-    }
+    const targetElement = e.target as HTMLElement | null
+    if (targetElement?.closest('[role="treeitem"]'))
+      return
 
-    // parentId from react-arborist is null for root, otherwise folder ID
-    executeMoveNode(nodeId, targetParentId)
-  }, [executeMoveNode, executeReorderNode, treeRef])
+    const draggedNode = tree.dragNode
+    if (!draggedNode)
+      return
+
+    const parentNode = dragTarget.parentId === null
+      ? tree.root
+      : tree.get(dragTarget.parentId)
+
+    commitInternalMove({
+      nodeId: draggedNode.id,
+      draggedNode,
+      parentId: dragTarget.parentId,
+      index: dragTarget.index,
+      parentNode,
+    })
+  }, [commitInternalMove, handleRootDrop])
 
   // react-arborist disableDrop callback - returns true to prevent drop
   const handleDisableDrop = useCallback((args: {
@@ -387,7 +438,7 @@ const FileTree = ({ className }: FileTreeProps) => {
           onDragEnter={handleRootDragEnter}
           onDragOver={handleRootDragOver}
           onDragLeave={handleRootDragLeave}
-          onDrop={handleRootDrop}
+          onDrop={handleTreeDrop}
         >
           <Tree<TreeNodeData>
             ref={treeRef}