🐛 fix(vscode): 文件树帮助模块改名，消除与 FileTree 组件仅大小写不同的冲突

macOS 文件系统不区分大小写，`./prFiles/FileTree` 会先命中 fileTree.ts，
导致 webview 类型检查失败、无法打包。

Claude-Session: https://claude.ai/code/session_01HTMgwaE3woqM5yvsHiuSAa

vscode/webview-ui/src/components/PrFilesPanel.tsx

@@ -17,7 +17,7 @@ import { usePrFiles } from '../hooks/usePrFiles'
 import { onMessage, postMessage } from '../lib/vscode'
 import { FileDiffPane } from './prFiles/FileDiffPane'
 import { FileTree } from './prFiles/FileTree'
-import { buildDirTree, flattenTree, isIgnoredPath } from './prFiles/fileTree'
+import { buildDirTree, flattenTree, isIgnoredPath } from './prFiles/fileTreeModel'
 
 interface PrFilesPanelProps {
   issue: Issue | null

vscode/webview-ui/src/components/prFiles/FileDiffPane.tsx

@@ -14,7 +14,7 @@ import { generateDiffFile } from '@git-diff-view/file'
 import { DiffModeEnum, DiffView } from '@git-diff-view/react'
 import { Check, Loader2, Sparkles } from 'lucide-react'
 import { useEffect, useLayoutEffect, useMemo, useRef, useState } from 'react'
-import { statusBadge, statusColorVar } from './fileTree'
+import { statusBadge, statusColorVar } from './fileTreeModel'
 import '@git-diff-view/react/styles/diff-view.css'
 
 interface FileDiffPaneProps {

vscode/webview-ui/src/components/prFiles/FileTree.tsx

@@ -5,10 +5,10 @@
  * 纯展示 + 回调:折叠态/选中态/已确认集合都由容器持有,本组件只发语义回调。
  */
 
-import type { TreeRow } from './fileTree'
+import type { TreeRow } from './fileTreeModel'
 import { Check, ChevronDown, ChevronRight, Folder } from 'lucide-react'
 import { useState } from 'react'
-import { statusBadge, statusColorVar } from './fileTree'
+import { statusBadge, statusColorVar } from './fileTreeModel'
 
 interface FileTreeProps {
   rows: TreeRow[]