feat(ui): render markdown in peek pane

- Add marked.js for full markdown rendering
- Stream peek body renders as markdown
- Card peek non-code content renders as markdown
- Code/snippet cards keep escaped pre/code display
- Styled: headers, lists, blockquotes, inline code, code blocks, links, hr
- Graceful fallback to escHtml if marked fails to load

web/app.js

@@ -768,7 +768,7 @@
         <span class="peek-brow-ts">${fmtDateLong(e.created_at)}</span>
       </div>
       ${e.title ? `<div class="peek-title" data-id="${e.id}">${escHtml(e.title)}</div>` : ''}
-      <div class="peek-body" data-id="${e.id}">${escHtml(e.body)}</div>
+      <div class="peek-body md" data-id="${e.id}">${renderMd(e.body)}</div>
       ${tags ? `<div class="peek-sec"><div class="peek-sec-lbl">tags</div><div class="peek-sec-inner tag-pills">${tags}</div></div>` : ''}
       <div class="peek-sec">
         <div class="peek-sec-lbl">context</div>
@@ -825,9 +825,13 @@
 
     if (!hasDecision && e.body) {
       const lang = data.lang || '';
+      const isCode = lang || e.card_type === 'snippet';
+      const bodyHtml = isCode
+        ? `<div class="peek-code"><pre><code>${escHtml(e.body)}</code></pre></div>`
+        : `<div class="peek-body md">${renderMd(e.body)}</div>`;
       sections += `<div class="peek-sec">
         <div class="peek-sec-lbl">content${lang ? `<span class="peek-sec-lang">${lang}</span>` : ''}${hasFill ? `<button class="peek-sec-run" onclick="nibApp.enterMode('fill')">⤓ fill</button>` : ''}</div>
-        <div class="peek-sec-inner"><div class="peek-code"><pre><code>${escHtml(e.body)}</code></pre></div></div>
+        <div class="peek-sec-inner">${bodyHtml}</div>
       </div>`;
     }
 
@@ -1629,6 +1633,12 @@
     return escHtml(s).replace(/'/g, '&#39;');
   }
 
+  function renderMd(s) {
+    if (!s) return '';
+    if (typeof marked === 'undefined') return escHtml(s);
+    return marked.parse(s, { breaks: true });
+  }
+
   function isSafeUrl(url) {
     return /^https?:\/\//i.test(url);
   }