chore: move src/llama_stack/ui to src/llama_stack_ui

# What does this PR do?


## Test Plan

src/llama_stack_ui/components/chat-playground/prompt-suggestions.tsx

@@ -0,0 +1,28 @@
+interface PromptSuggestionsProps {
+  label: string;
+  append: (message: { role: "user"; content: string }) => void;
+  suggestions: string[];
+}
+
+export function PromptSuggestions({
+  label,
+  append,
+  suggestions,
+}: PromptSuggestionsProps) {
+  return (
+    <div className="space-y-6">
+      <h2 className="text-center text-2xl font-bold">{label}</h2>
+      <div className="flex gap-6 text-sm">
+        {suggestions.map(suggestion => (
+          <button
+            key={suggestion}
+            onClick={() => append({ role: "user", content: suggestion })}
+            className="h-max flex-1 rounded-xl border bg-background p-4 hover:bg-muted"
+          >
+            <p>{suggestion}</p>
+          </button>
+        ))}
+      </div>
+    </div>
+  );
+}