Rename block .editor files to .config

Also drop the color and leftSideBarVisible overrides from PageEditor.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014xjLo7mFxZXfPDCHuKX4Dz

components/shopify/store-assistant.config.tsx

@@ -0,0 +1,16 @@
+import { ComponentConfig } from '@reacteditor/core';
+import { MessageCircle } from 'lucide-react';
+import StoreAssistant from '@/components/shopify/store-assistant';
+
+export type StoreAssistantBlockProps = Record<string, never>;
+
+const storeAssistantEditor: ComponentConfig<StoreAssistantBlockProps> = {
+  label: 'Store assistant',
+  icon: <MessageCircle size={16} />,
+  category: 'content',
+  defaultProps: {},
+  fields: {},
+  render: () => <StoreAssistant />,
+};
+
+export default storeAssistantEditor;