fix(explorer): 非文件拖拽不再触发文件树上传遮罩 (#317)

拖动 Tab（重排/跨 pane split）经过资源管理器文件树时，FileTree 的
dragenter/dragover/drop 此前对任何拖拽都响应：显示上传遮罩并吞掉
事件，导致 pane 根的 Tab-drop 处理收不到、Tab 无法落下。

统一按 dataTransfer.types 含 'Files' 门控（与 Sidebar.tsx 面板宿主
shield 一致）：非文件拖拽原样冒泡给 pane 根，OS 文件拖拽行为不变。

回归测试：应用内 Tab 拖拽不出现 uploadDropZone、不改 dropTarget、
不 preventDefault、不触发 onUploadRequest。

src/client/FileTree.tsx

@@ -52,6 +52,13 @@ function parentOf(path: string): string {
   return at <= 0 ? path : path.slice(0, at)
 }
 
+/** Only OS file drags belong to the upload surface; in-app drags (tab reorder,
+ *  split zones) must pass through untouched to the pane's tab-drop handling
+ *  (mirror of Sidebar.tsx's panel-host shield gate). */
+function isFileDrag(event: DragEvent): boolean {
+  return event.dataTransfer?.types.includes('Files') ?? false
+}
+
 /** How long the row's "copied" label stays after a successful write. */
 const COPIED_MS = 1200
 
@@ -160,12 +167,14 @@ export function FileTree(props: {
     })
   }
   const handleBodyDrop = (event: DragEvent): void => {
+    if (!isFileDrag(event)) return
     event.preventDefault()
     event.stopPropagation()
     resetDrop()
     if (cwd !== undefined) reportDrop(cwd, event.dataTransfer)
   }
   const handleDirDrop = (event: DragEvent, dir: string): void => {
+    if (!isFileDrag(event)) return
     event.preventDefault()
     event.stopPropagation()
     resetDrop()
@@ -176,6 +185,7 @@ export function FileTree(props: {
     handleDirDrop(event, parentOf(path))
   }
   const handleBodyDragEnter = (event: DragEvent): void => {
+    if (!isFileDrag(event)) return
     event.preventDefault()
     event.stopPropagation()
     dropDepth.current += 1
@@ -195,6 +205,7 @@ export function FileTree(props: {
     setDropRect(null)
   }
   const handleBodyDragOver = (event: DragEvent): void => {
+    if (!isFileDrag(event)) return
     event.preventDefault()
     event.stopPropagation()
     event.dataTransfer.dropEffect = busy ? 'none' : 'copy'
@@ -205,6 +216,7 @@ export function FileTree(props: {
     setDropTarget(null)
   }
   const handleRowDragOver = (event: DragEvent, dir: string): void => {
+    if (!isFileDrag(event)) return
     event.preventDefault()
     event.stopPropagation()
     event.dataTransfer.dropEffect = busy ? 'none' : 'copy'

tests/file-tree-drop.spec.tsx

@@ -14,6 +14,7 @@ import { createElement } from 'react'
 import { createRoot, type Root } from 'react-dom/client'
 import { act } from 'react-dom/test-utils'
 import { FileTree } from '../src/client/FileTree.tsx'
+import { TAB_DRAG_TYPE } from '../src/client/TabBar.tsx'
 import type { UploadItem } from '../src/client/upload.ts'
 
 // The act() environment flag (React 18.2 reads it before flushing effects).
@@ -72,12 +73,12 @@ async function mountTree(busy = false): Promise<Harness> {
 }
 
 /** A bubbling drag event carrying a stub dataTransfer (jsdom has no DragEvent). */
-function dragEvent(type: string): Event {
+function dragEvent(type: string, dataTypes: string[] = ['Files']): Event {
   const event = new Event(type, { bubbles: true, cancelable: true })
   Object.defineProperty(event, 'dataTransfer', {
     // No entry API on the items, so drops fall back to the flat file list.
     value: {
-      types: ['Files'],
+      types: dataTypes,
       items: [],
       files: [new File(['x'], 'dropped.txt')],
       dropEffect: '',
@@ -87,8 +88,8 @@ function dragEvent(type: string): Event {
 }
 
 /** Dispatch inside act() so React flushes the state update. */
-function fire(target: Element, type: string): Event {
-  const event = dragEvent(type)
+function fire(target: Element, type: string, dataTypes?: string[]): Event {
+  const event = dragEvent(type, dataTypes)
   act(() => { target.dispatchEvent(event) })
   return event
 }
@@ -179,4 +180,26 @@ describe('FileTree drag-drop surface', () => {
     expect(busyHarness.uploads).toHaveLength(0)
     busyHarness.unmount()
   })
+
+  it('ignores an in-app tab drag: no upload drop zone and events pass through', () => {
+    const enter = fire(harness.body, 'dragenter', [TAB_DRAG_TYPE])
+    expect(enter.defaultPrevented).toBe(false)
+    expect(dropZone()).toBeNull()
+    const over = fire(harness.body, 'dragover', [TAB_DRAG_TYPE])
+    expect(over.defaultPrevented).toBe(false)
+    expect(dropZone()).toBeNull()
+    // A row hover must not retarget the drop directory either.
+    const dir = rowByName(harness.container, 'src')
+    const rowOver = fire(dir, 'dragover', [TAB_DRAG_TYPE])
+    expect(rowOver.defaultPrevented).toBe(false)
+    expect(dir.className).not.toContain('explorerRowDropTarget')
+  })
+
+  it('passes an in-app tab drop through without reporting an upload', async () => {
+    const drop = fire(harness.body, 'drop', [TAB_DRAG_TYPE])
+    await act(async () => {})
+    expect(drop.defaultPrevented).toBe(false)
+    expect(harness.uploads).toHaveLength(0)
+    expect(dropZone()).toBeNull()
+  })
 })