chore: move src/llama_stack/ui to src/llama_stack_ui (#4068)

# What does this PR do?
This better separates UI from backend code, which was a point of
confusion often for our beloved AI friends.


## Test Plan
CI

src/llama_stack_ui/components/ui/copy-button.tsx

@@ -0,0 +1,44 @@
+"use client";
+
+import { Check, Copy } from "lucide-react";
+
+import { cn } from "@/lib/utils";
+import { useCopyToClipboard } from "@/hooks/use-copy-to-clipboard";
+import { Button } from "@/components/ui/button";
+
+type CopyButtonProps = {
+  content: string;
+  copyMessage?: string;
+};
+
+export function CopyButton({ content, copyMessage }: CopyButtonProps) {
+  const { isCopied, handleCopy } = useCopyToClipboard({
+    text: content,
+    copyMessage,
+  });
+
+  return (
+    <Button
+      variant="ghost"
+      size="icon"
+      className="relative h-6 w-6"
+      aria-label="Copy to clipboard"
+      onClick={handleCopy}
+    >
+      <div className="absolute inset-0 flex items-center justify-center">
+        <Check
+          className={cn(
+            "h-4 w-4 transition-transform ease-in-out",
+            isCopied ? "scale-100" : "scale-0"
+          )}
+        />
+      </div>
+      <Copy
+        className={cn(
+          "h-4 w-4 transition-transform ease-in-out",
+          isCopied ? "scale-0" : "scale-100"
+        )}
+      />
+    </Button>
+  );
+}