make show stats work when only one file changed (#32244) (#32268)

Backport #32244

fix #32226

in #27775 , it do some changes to
only show diff file tree when more than one file changed. But looks it
also break the `diff-file-list` logic, which looks not expected change.
so try fix it.

/cc @silverwind

example view:

![image](https://github.com/user-attachments/assets/281e9c4f-a269-4d36-94eb-a132058aea87)

Signed-off-by: a1012112796 <1012112796@qq.com>

web_src/js/features/repo-diff-filetree.js

@@ -8,7 +8,9 @@ export function initDiffFileTree() {
 
   const fileTreeView = createApp(DiffFileTree);
   fileTreeView.mount(el);
+}
 
+export function initDiffFileList() {
   const fileListElement = document.getElementById('diff-file-list');
   if (!fileListElement) return;
 

web_src/js/features/repo-diff.js

@@ -1,7 +1,7 @@
 import $ from 'jquery';
 import {initCompReactionSelector} from './comp/ReactionSelector.js';
 import {initRepoIssueContentHistory} from './repo-issue-content.js';
-import {initDiffFileTree} from './repo-diff-filetree.js';
+import {initDiffFileTree, initDiffFileList} from './repo-diff-filetree.js';
 import {initDiffCommitSelect} from './repo-diff-commitselect.js';
 import {validateTextareaNonEmpty} from './comp/ComboMarkdownEditor.js';
 import {initViewedCheckboxListenerFor, countAndUpdateViewedFiles, initExpandAndCollapseFilesButton} from './pull-view-file.js';
@@ -220,6 +220,7 @@ export function initRepoDiffView() {
   initRepoDiffConversationForm();
   if (!$('#diff-file-list').length) return;
   initDiffFileTree();
+  initDiffFileList();
   initDiffCommitSelect();
   initRepoDiffShowMore();
   initRepoDiffReviewButton();