Replace marked.min.js with the marked npm package and update all references accordingly.

src/popup.js

@@ -1,6 +1,8 @@
 // popup.js
 "use strict";
 
+import { marked } from "marked";
+
 // ── State ───────────────────────────────────────────────────────────────────
 const state = {
   markdown: "",
@@ -172,12 +174,7 @@ function sanitizeHtml(html) {
 
 function renderPreview() {
   state.markdown = mdEditor.value;
-  if (typeof marked !== "undefined") {
-    mdPreview.innerHTML = sanitizeHtml(marked.parse(state.markdown, { breaks: true }));
-  } else {
-    // Fallback: basic escaping
-    mdPreview.innerHTML = `<pre style="white-space:pre-wrap">${escHtml(state.markdown)}</pre>`;
-  }
+  mdPreview.innerHTML = sanitizeHtml(marked.parse(state.markdown, { breaks: true }));
 }
 
 function escHtml(s) {