Convert frontend code to typescript (#31559)

None of the frontend js/ts files was touched besides these two commands
(edit: no longer true, I touched one file in
61105d0618
because of a deprecation that was not showing before the rename).

`tsc` currently reports 778 errors, so I have disabled it in CI as
planned.

Everything appears to work fine.

web_src/js/features/repo-wiki.ts

@@ -0,0 +1,89 @@
+import {initMarkupContent} from '../markup/content.ts';
+import {validateTextareaNonEmpty, initComboMarkdownEditor} from './comp/ComboMarkdownEditor.ts';
+import {fomanticMobileScreen} from '../modules/fomantic.ts';
+import {POST} from '../modules/fetch.ts';
+
+async function initRepoWikiFormEditor() {
+  const editArea = document.querySelector('.repository.wiki .combo-markdown-editor textarea');
+  if (!editArea) return;
+
+  const form = document.querySelector('.repository.wiki.new .ui.form');
+  const editorContainer = form.querySelector('.combo-markdown-editor');
+  let editor;
+
+  let renderRequesting = false;
+  let lastContent;
+  const renderEasyMDEPreview = async function () {
+    if (renderRequesting) return;
+
+    const previewFull = editorContainer.querySelector('.EasyMDEContainer .editor-preview-active');
+    const previewSide = editorContainer.querySelector('.EasyMDEContainer .editor-preview-active-side');
+    const previewTarget = previewSide || previewFull;
+    const newContent = editArea.value;
+    if (editor && previewTarget && lastContent !== newContent) {
+      renderRequesting = true;
+      const formData = new FormData();
+      formData.append('mode', editor.previewMode);
+      formData.append('context', editor.previewContext);
+      formData.append('text', newContent);
+      formData.append('wiki', editor.previewWiki);
+      try {
+        const response = await POST(editor.previewUrl, {data: formData});
+        const data = await response.text();
+        lastContent = newContent;
+        previewTarget.innerHTML = `<div class="markup ui segment">${data}</div>`;
+        initMarkupContent();
+      } catch (error) {
+        console.error('Error rendering preview:', error);
+      } finally {
+        renderRequesting = false;
+        setTimeout(renderEasyMDEPreview, 1000);
+      }
+    } else {
+      setTimeout(renderEasyMDEPreview, 1000);
+    }
+  };
+  renderEasyMDEPreview();
+
+  editor = await initComboMarkdownEditor(editorContainer, {
+    useScene: 'wiki',
+    // EasyMDE has some problems of height definition, it has inline style height 300px by default, so we also use inline styles to override it.
+    // And another benefit is that we only need to write the style once for both editors.
+    // TODO: Move height style to CSS after EasyMDE removal.
+    editorHeights: {minHeight: '300px', height: 'calc(100vh - 600px)'},
+    previewMode: 'gfm',
+    previewWiki: true,
+    easyMDEOptions: {
+      previewRender: (_content, previewTarget) => previewTarget.innerHTML, // disable builtin preview render
+      toolbar: ['bold', 'italic', 'strikethrough', '|',
+        'heading-1', 'heading-2', 'heading-3', 'heading-bigger', 'heading-smaller', '|',
+        'gitea-code-inline', 'code', 'quote', '|', 'gitea-checkbox-empty', 'gitea-checkbox-checked', '|',
+        'unordered-list', 'ordered-list', '|',
+        'link', 'image', 'table', 'horizontal-rule', '|',
+        'preview', 'fullscreen', 'side-by-side', '|', 'gitea-switch-to-textarea',
+      ],
+    },
+  });
+
+  form.addEventListener('submit', (e) => {
+    if (!validateTextareaNonEmpty(editArea)) {
+      e.preventDefault();
+      e.stopPropagation();
+    }
+  });
+}
+
+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();
+}