Replace Trix with Lexxy

app/javascript/models/message_formatter.js

@@ -76,7 +76,20 @@ export default class MessageFormatter {
   }
 
   #highlightCodeBlock(block) {
-    if (this.#isPlainText(block)) window.hljs.highlightElement(block)
+    this.#normalizeLineBreaks(block)
+    if (!this.#isPlainText(block)) return
+
+    const language = block.dataset.language
+    if (language && window.hljs.getLanguage(language)) {
+      block.classList.add(`language-${language}`)
+    }
+
+    window.hljs.highlightElement(block)
+  }
+
+  // Lexxy breaks code block lines with <br>, Trix-era blocks used newlines
+  #normalizeLineBreaks(block) {
+    block.querySelectorAll("br").forEach(br => br.replaceWith("\n"))
   }
 
   #isPlainText(element) {