feat(core): add an independent AI panel (#13004)

close AI-246, AI-285
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

## Summary by CodeRabbit

* **New Features**
* Introduced an AI chat interface accessible from the sidebar with a
dedicated "/chat" route.
* Added "AFFiNE Intelligent" button with AI icon to the sidebar for
quick chat access.
* Enhanced chat components with an "independent mode" for improved
message display and layout.
* Improved chat input and content styling, including responsive layout
and onboarding offset support.

* **Improvements**
  * Expanded icon support to include an AI icon in the app.
* Updated utility and schema functions for greater flexibility and error
prevention.
* Added a new chat container style for consistent layout and max width.

* **Bug Fixes**
* Prevented potential errors when certain editor hosts are not provided.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/components/root-app-sidebar/index.tsx

@@ -18,6 +18,7 @@ import { useI18n } from '@affine/i18n';
 import { track } from '@affine/track';
 import type { Store } from '@blocksuite/affine/store';
 import {
+  AiIcon,
   AllDocsIcon,
   ImportIcon,
   JournalIcon,
@@ -86,6 +87,22 @@ const AllDocsButton = () => {
   );
 };
 
+const AIChatButton = () => {
+  const { workbenchService } = useServices({
+    WorkbenchService,
+  });
+  const workbench = workbenchService.workbench;
+  const aiChatActive = useLiveData(
+    workbench.location$.selector(location => location.pathname === '/chat')
+  );
+
+  return (
+    <MenuLinkItem icon={<AiIcon />} active={aiChatActive} to={'/chat'}>
+      <span data-testid="ai-chat">AFFiNE Intelligent</span>
+    </MenuLinkItem>
+  );
+};
+
 /**
  * This is for the whole affine app sidebar.
  * This component wraps the app sidebar in `@affine/component` with logic and data.
@@ -184,6 +201,7 @@ export const RootAppSidebar = memo((): ReactElement => {
         <AllDocsButton />
         <AppSidebarJournalButton />
         {sessionStatus === 'authenticated' && <NotificationButton />}
+        <AIChatButton />
         <MenuItem
           data-testid="slider-bar-workspace-setting-button"
           icon={<SettingsIcon />}