tidy up header

apps/app/src/features/openai/chat/components/AiChatModal/AiChatModal.module.scss

@@ -1,4 +1,5 @@
 @use '@growi/core-styles/scss/bootstrap/init' as bs;
+@use '@growi/core-styles/scss/variables/growi-official-colors';
 @use '@growi/ui/scss/atoms/btn-muted';
 
 .rag-search-modal :global {
@@ -15,6 +16,10 @@
 
 // == Colors
 .rag-search-modal :global {
+  .growi-ai-chat-icon {
+    color: growi-official-colors.$growi-ai-purple;
+  }
+
   .btn-submit {
     @include btn-muted.colorize(bs.$purple, bs.$purple);
   }

apps/app/src/features/openai/chat/components/AiChatModal/AiChatModal.tsx

@@ -218,8 +218,9 @@ export const AiChatModal = (): JSX.Element => {
     <Modal size="lg" isOpen={isOpened} toggle={closeRagSearchModal} className={moduleClass} scrollable>
 
       <ModalHeader tag="h4" toggle={closeRagSearchModal} className="pe-4">
-        <span className="material-symbols-outlined text-primary">psychology</span>
-        GROWI Assistant
+        <span className="material-symbols-outlined growi-ai-chat-icon me-3">chat</span>
+        <span className="fw-bold">GROWI Assistant</span>
+        <span className="fs-5 text-body-secondary ms-3">(Beta)</span>
       </ModalHeader>
 
       { isOpened && (