fix: aspec ratio of rendering

frontend/src/components/nodes/RenderingNode.tsx

@@ -539,6 +539,23 @@ function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
     // Kroki and other SVG sources may prepend <?xml ... ?> so we detect by presence of <svg> tag
     const isSvgOutput = Boolean(renderedContent?.trim() && /<svg[\s>]/i.test(renderedContent.trim()))
 
+    /** Process SVG HTML so it keeps aspect ratio and fills the viewport (used only for display, not download). */
+    const displayContent = useMemo(() => {
+        if (!renderedContent || !isSvgOutput) return renderedContent
+        let html = renderedContent
+        // Force preserve aspect ratio so the diagram is not stretched (Kroki often returns preserveAspectRatio="none")
+        html = html.replace(/\bpreserveAspectRatio\s*=\s*["']none["']/gi, 'preserveAspectRatio="xMidYMid meet"')
+        // Make root SVG fill container so it scales uniformly with meet
+        html = html.replace(/\bwidth\s*=\s*["'][^"']*["']/i, 'width="100%"')
+        html = html.replace(/\bheight\s*=\s*["'][^"']*["']/i, 'height="100%"')
+        // Override inline style width/height so they don't override the attributes
+        html = html.replace(/\bstyle\s*=\s*["']([^"']*)["']/i, (_, style) => {
+            const overridden = style.replace(/\b(width|height):[^;]+/gi, '$1:100%')
+            return `style="${overridden}"`
+        })
+        return html
+    }, [renderedContent, isSvgOutput])
+
     const downloadSvg = useCallback(() => {
         if (!renderedContent || !isSvgOutput) return
         const blob = new Blob([renderedContent], { type: 'image/svg+xml' })
@@ -872,14 +889,14 @@ function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
                                                         <RotateCcw className="size-3 max-w-[12px] max-h-[12px]" />
                                                     </button>
                                                 </div>
-                                                <div className="absolute inset-0 nodrag nopan overflow-hidden">
+                                                <div className="absolute inset-0 nodrag nopan overflow-hidden flex flex-col">
                                                     <TransformComponent
                                                         wrapperClass="!w-full !h-full"
-                                                        contentClass="inline-flex nodrag nopan"
+                                                        contentClass="inline-flex flex-col nodrag nopan !w-full !min-h-0 !flex-1"
                                                     >
                                                         <div
-                                                            className="rendering-diagram inline-flex p-4 nodrag nopan"
+                                                            className="rendering-diagram inline-flex w-full min-h-0 flex-1 p-4 nodrag nopan"
-                                                            dangerouslySetInnerHTML={{ __html: renderedContent }}
+                                                            dangerouslySetInnerHTML={{ __html: displayContent ?? '' }}
                                                         />
                                                     </TransformComponent>
                                                 </div>