Protect code spans when stripping HTML tags in mobile preview

Ensure HTML-like content within code spans is not erroneously removed
by the tag stripping logic. We now protect markdown code blocks and
restore them after stripping tags and decoding HTML entities.

mobile/src/components/MobileMarkdown.test.ts

@@ -80,6 +80,9 @@ describe('parseMobileMarkdown', () => {
     expect(normalizeMobileMarkdownPreviewHtml('<p>Use <code>Array&lt;string&gt;</code></p>')).toBe(
       'Use `Array<string>`'
     )
+    expect(
+      normalizeMobileMarkdownPreviewHtml('<p>Use <code>&lt;div&gt;x&lt;/div&gt;</code></p>')
+    ).toBe('Use `<div>x</div>`')
   })
 
   it('does not replace literal code placeholder text in markdown prose', () => {

mobile/src/components/mobile-markdown-preview-html.ts

@@ -50,8 +50,9 @@ function decodeHtmlEntities(value: string, preserveEscapedEntities = false): str
 }
 
 function stripTags(value: string): string {
-  return decodeHtmlEntities(
-    value
+  const { protectedText, codeSpans, placeholderPrefix } = protectMarkdownCode(value)
+  const stripped = decodeHtmlEntities(
+    protectedText
       .replace(/<!--[\s\S]*?-->/g, '')
       .replace(/<\/?([A-Za-z][A-Za-z0-9:-]*)(?:\s[^<>]*)?\/?>/g, (tag, name: string) =>
         strippableHtmlTagNames.has(name.toLowerCase()) ? '' : tag
@@ -61,6 +62,8 @@ function stripTags(value: string): string {
     .replace(/[ \t]+\n/g, '\n')
     .replace(/\n{3,}/g, '\n\n')
     .trim()
+
+  return restoreMarkdownCode(stripped, codeSpans, placeholderPrefix)
 }
 
 function attrValue(tag: string, name: string): string {