feat: codeblock add copy button when hover.

src/components/ChatInterface.jsx

@@ -213,12 +213,74 @@ const markdownComponents = {
         </code>
       );
     }
+    const [copied, setCopied] = React.useState(false);
+    const textToCopy = raw;
+
+    const handleCopy = () => {
+      const doSet = () => {
+        setCopied(true);
+        setTimeout(() => setCopied(false), 1500);
+      };
+      try {
+        if (navigator && navigator.clipboard && navigator.clipboard.writeText) {
+          navigator.clipboard.writeText(textToCopy).then(doSet).catch(() => {
+            // Fallback
+            const ta = document.createElement('textarea');
+            ta.value = textToCopy;
+            ta.style.position = 'fixed';
+            ta.style.opacity = '0';
+            document.body.appendChild(ta);
+            ta.select();
+            try { document.execCommand('copy'); } catch {}
+            document.body.removeChild(ta);
+            doSet();
+          });
+        } else {
+          const ta = document.createElement('textarea');
+          ta.value = textToCopy;
+          ta.style.position = 'fixed';
+          ta.style.opacity = '0';
+          document.body.appendChild(ta);
+          ta.select();
+          try { document.execCommand('copy'); } catch {}
+          document.body.removeChild(ta);
+          doSet();
+        }
+      } catch {}
+    };
+
     return (
-      <pre className="bg-gray-900 dark:bg-gray-900 border border-gray-700/40 rounded-lg p-3 overflow-x-auto my-2">
+      <div className="relative group my-2">
+        <button
+          type="button"
+          onClick={handleCopy}
+          className="absolute top-2 right-2 z-10 opacity-0 group-hover:opacity-100 focus:opacity-100 active:opacity-100 transition-opacity text-xs px-2 py-1 rounded-md bg-gray-700/80 hover:bg-gray-700 text-white border border-gray-600"
+          title={copied ? 'Copied' : 'Copy code'}
+          aria-label={copied ? 'Copied' : 'Copy code'}
+        >
+          {copied ? (
+            <span className="flex items-center gap-1">
+              <svg className="w-3.5 h-3.5" viewBox="0 0 20 20" fill="currentColor">
+                <path fillRule="evenodd" d="M16.707 5.293a1 1 0 010 1.414l-8 8a1 1 0 01-1.414 0l-4-4a1 1 0 011.414-1.414L8 12.586l7.293-7.293a1 1 0 011.414 0z" clipRule="evenodd" />
+              </svg>
+              Copied
+            </span>
+          ) : (
+            <span className="flex items-center gap-1">
+              <svg className="w-3.5 h-3.5" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
+                <rect x="9" y="9" width="13" height="13" rx="2" ry="2"></rect>
+                <path d="M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1"></path>
+              </svg>
+              Copy
+            </span>
+          )}
+        </button>
+        <pre className="bg-gray-900 dark:bg-gray-900 border border-gray-700/40 rounded-lg p-3 overflow-x-auto">
           <code className={`text-gray-100 dark:text-gray-100 text-sm font-mono ${className || ''}`} {...props}>
             {children}
           </code>
         </pre>
+      </div>
     );
   },
   blockquote: ({ children }) => (