fix(renderer): prevent welcome screen from overwriting opened markdown files

The welcome tab setup awaited getAppVersion() inside DOMContentLoaded.
While yielding, the renderer-ready timeout fired, file-opened was processed,
and openFile rendered the markdown. When the welcome setup resumed, it
overwrote tab.content and preview.innerHTML with the welcome screen,
leaving the preview blank.

Fix: only show the welcome screen if the tab is still empty (no filePath
and no content) when the async setup resumes.

Amit Haridas

src/renderer.js

@@ -1730,7 +1730,8 @@ document.addEventListener('DOMContentLoaded', async () => {
         const welcomeHtml = getCreateWelcomeContent()(recentFiles, appVersion);
 
         const tab = tabManager.tabs.get(tabManager.activeTabId);
-        if (tab) {
+        // Only show welcome if no file was opened while we were awaiting
+        if (tab && !tab.filePath && tab.content === '') {
             tab.title = 'Welcome';
             tab.content = '';
             const preview = document.getElementById(`preview-${tab.id}`);