Improve wiki sidebar and TOC (#25460)

Close #20976
Close #20975

1. Fix the bug: the TOC in footer was incorrectly rendered as main
content's TOC
2. Fix the layout: on mobile, the TOC is put above the main content,
while the sidebar is put below the main content
3. Auto collapse the TOC on mobile

ps: many styles of "wiki.css" are moved from old css files, so leave
nits to following PRs.

web_src/js/features/repo-wiki.js

@@ -1,6 +1,7 @@
 import $ from 'jquery';
 import {initMarkupContent} from '../markup/content.js';
 import {validateTextareaNonEmpty, initComboMarkdownEditor} from './comp/ComboMarkdownEditor.js';
+import {fomanticMobileScreen} from '../modules/fomantic.js';
 
 const {csrfToken} = window.config;
 
@@ -70,6 +71,17 @@ async function initRepoWikiFormEditor() {
   });
 }
 
+function collapseWikiTocForMobile(collapse) {
+  if (collapse) {
+    document.querySelector('.wiki-content-toc details')?.removeAttribute('open');
+  }
+}
+
 export function initRepoWikiForm() {
+  if (!document.querySelector('.page-content.repository.wiki')) return;
+
+  fomanticMobileScreen.addEventListener('change', (e) => collapseWikiTocForMobile(e.matches));
+  collapseWikiTocForMobile(fomanticMobileScreen.matches);
+
   initRepoWikiFormEditor();
 }

web_src/js/modules/fomantic.js

@@ -3,6 +3,8 @@ import {initAriaCheckboxPatch} from './aria/checkbox.js';
 import {initAriaDropdownPatch} from './aria/dropdown.js';
 import {svg} from '../svg.js';
 
+export const fomanticMobileScreen = window.matchMedia('only screen and (max-width: 767.98px)');
+
 export function initGiteaFomantic() {
   // Silence fomantic's error logging when tabs are used without a target content element
   $.fn.tab.settings.silent = true;