fix: add LINE_BREAK_VISUAL const

Author: S-FrontendDev

src/lib/markdown.js

@@ -4,7 +4,11 @@ import DOMPurify from 'dompurify'
 
 // The U+2028 character (LINE SEPARATOR) is sometimes used as a line break, but it is treated as a space in some web environments,
 // causing unexpected rendering issues. To avoid this, it's recommended to replace it with a standard line break character such as `\n`.
-const LINE_SEPARATOR = /\u2028/g;
+const LINE_SEPARATOR = /\u2028/g
+
+// LINE_BREAK_VISUAL is used for formatting when the message is displayed as a single line in a preview.
+// It replaces line breaks with a visual symbol (↵) to indicate where new lines exist in the original text.
+const LINE_BREAK_VISUAL =  '↵ '
 
 marked.setOptions({
   // marked sanitize is deprecated, using DOMPurify
@@ -73,14 +77,12 @@ export function removeFormats(text = '') {
 export function formatMessage(text = '') {
   const node = document.createElement('div')
 
-  const replaceValue = '↵ '
-
-  const textWithSymbol = text.replace(/\n/g, replaceValue)
+  const textWithSymbol = text.replace(/\n/g, LINE_BREAK_VISUAL)
   node.innerHTML = marked.parse(sanitizeHTML(textWithSymbol))
 
   const textWithoutHtml = node.textContent || node.innerText || ''
 
   return textWithoutHtml
-    .replace(LINE_SEPARATOR, replaceValue)
+    .replace(LINE_SEPARATOR, LINE_BREAK_VISUAL)
     .replace(/↵/g, '<span class="arrow-return">↵</span>')
 }