feat(editor): add scroll navigation and update theme Markdown behavior

frontend/src/features/themes/CommunityThemePreview.vue

@@ -6,6 +6,7 @@ import { getCommunityThemePreviewCss, mockCommunityThemes } from '@/services/the
 import tokensCss from '@/styles/tokens.css?raw'
 import featuresCss from '@/styles/features.css?raw'
 import headingsCss from '@/styles/headings.css?raw'
+import markdownBehaviorCss from '@/styles/markdown-behavior.css?raw'
 import calloutsCss from '@/styles/callouts.css?raw'
 import { calloutTypes } from '@/utils/callouts'
 import specimenHtml from './themeSpecimen.html?raw'
@@ -25,6 +26,7 @@ const previewDocument = computed(() => {
   const style = doc.createElement('style')
   style.textContent = `${tokensCss}\n${featuresCss}\n${calloutsCss}\n${headingsCss}\n${props.css ?? getCommunityThemePreviewCss(props.themeId)}\nhtml { height:100% !important; overflow-y:auto !important; overflow-x:hidden !important; overscroll-behavior:contain; } body { height:auto !important; min-height:100%; overflow:visible !important; margin:0; padding:24px; background:var(--color-background-primary); color:var(--color-text-primary); font:16px/1.6 system-ui; } article { min-width:0; } .theme-specimen { display:grid; gap:16px; margin-top:20px; } .surface-nested { padding:12px; border:1px solid var(--color-border-default); border-radius:var(--radius-md); } .specimen-markdown { overflow:auto; } .specimen-markdown code { background:var(--color-code-background, var(--color-background-secondary)); color:var(--color-code-text, var(--color-text-primary)); padding:3px 6px; border-radius:4px; } .specimen-markdown pre { padding:12px; background:var(--color-background-secondary); } .specimen-markdown blockquote { border-left:3px solid var(--color-accent-primary); padding-left:12px; } .specimen-markdown table { width:100%; border-collapse:collapse; } .specimen-markdown td,.specimen-markdown th { padding:8px; border:1px solid var(--color-border-default); } .specimen-markdown th { background:var(--color-markdown-table-header); } .specimen-chart > div { display:flex; align-items:flex-end; gap:12px; height:100px; border-bottom:1px solid var(--color-border-default); } .specimen-chart span { width:36px; } .specimen-long { overflow-wrap:anywhere; } @media(max-width:480px) { body { padding:12px; } .form-grid { grid-template-columns:minmax(0,1fr); } }`
 
+  style.textContent += `\n${markdownBehaviorCss}\n.specimen-scroll { position:relative; min-height:110px; }`
   doc.head.append(style)
   const article = doc.createElement('article')
   article.className = 'panel'