PPTX Viewer

Differences from upstream

• Upstream exports PptxViewerPreview and PptxViewerPreviewProps; both are available here, plus PptxViewer and PptxViewerProps.
• Exported as both PptxViewer and the upstream name PptxViewerPreview; className and class are both accepted.
• Slides render with the pptx-browser engine instead of @extend-ai/react-pptx (React-only), as one virtualized list.
• Not ported: defaultZoom and the zoom controls, the thumbnail sidebar (defaultThumbnailSidebarOpen), and slide navigation (initialSlide, jump to slide, keyboard navigation).
• Upload accepts .pptx only; legacy .ppt files cannot be read by the engine.
• toolbarActions is a Svelte snippet instead of a React node.
• Dark mode is set by the parent through isDark (upstream follows the app theme). The viewer has no theme switch of its own, so onIsDarkChange is never called.
• Port additions: height, slideHeight, slideWidth, and overscan size the fixed-row virtual list.