fix multiple renders of the same mermaid diagram (vercel#59)

* Improve stable ID

* Update mermaid.tsx

* Create social-bugs-doubt.md

Author: haydenbleasel

.changeset/social-bugs-doubt.md

@@ -0,0 +1,5 @@
+---
+"streamdown": patch
+---
+
+fix multiple renders of the same mermaid diagram

apps/website/app/components/mermaid.tsx

@@ -1,7 +1,7 @@
 import { Section } from './section';
 
 export const MermaidDemo = () => {
-  const mermaidExample = `Interactive diagram rendering with manual control. Click the chart icon next to any Mermaid code block to render it!
+  const mermaidExample = `Interactive diagram rendering with manual control. Click the copy icon next to any Mermaid diagram to copy the code to your clipboard.
 
 ## Simple Flowchart
 

packages/streamdown/lib/mermaid.tsx

@@ -46,12 +46,12 @@ export const Mermaid = ({ chart, className }: MermaidProps) => {
         // Initialize mermaid only once globally
         const mermaid = await initializeMermaid();
 
-        // Use a stable ID based on chart content hash to prevent re-renders
+        // Use a stable ID based on chart content hash and timestamp to ensure uniqueness
         const chartHash = chart.split('').reduce((acc, char) => {
           // biome-ignore lint/suspicious/noBitwiseOperators: "Required for Mermaid"
           return ((acc << 5) - acc + char.charCodeAt(0)) | 0;
         }, 0);
-        const uniqueId = `mermaid-${Math.abs(chartHash)}`;
+        const uniqueId = `mermaid-${Math.abs(chartHash)}-${Date.now()}-${Math.random().toString(36).substring(2, 9)}`;
 
         const { svg } = await mermaid.render(uniqueId, chart);