fix: pass markdown theme to preloadContentLanguages for correct shiki initialization

preloadContentLanguages initialized the shiki highlighter with default
themes (vitesse-light/vitesse-dark) because it never received the user's
configured theme. When renderMarkdown later called codeToHast with the
actual theme, the highlighter didn't have it loaded, silently falling
back to plain text for all code blocks.

Author: Priestch

packages/markopress/src/build/index.ts

@@ -310,7 +310,7 @@ export async function build(options: BuildOptions = {}): Promise<BuildResult> {
     console.log('   Public assets synced\n');
 
     // Preload syntax highlighting languages from content + config
-    await preloadContentLanguages(modules, config.markdown?.languages, debug);
+    await preloadContentLanguages(modules, config.markdown?.languages, debug, config.markdown?.theme);
 
     // Step 4a: Build search index
     if (config.search?.enabled !== false) {

packages/markopress/src/markdown/loader.ts

@@ -465,8 +465,13 @@ export function scanCodeBlockLanguages(content: string): string[] {
 export async function preloadContentLanguages(
   modules: Array<{ files: Array<{ filePath: string }> }>,
   configLanguages: string[] = [],
-  debug = false
+  debug = false,
+  theme?: { light?: string; dark?: string }
 ): Promise<void> {
+  // Ensure highlighter is initialized with the correct theme before loading languages
+  if (!highlighterInstance && theme) {
+    await getHighlighterInstance(theme);
+  }
   const scannedLanguages = new Set<string>();
   for (const mod of modules) {
     for (const file of mod.files) {