feat(chat): enhance sidebar with session management and deletion (#274)

src/pages/Chat/ChatToolbar.tsx

@@ -3,7 +3,7 @@
  * Session selector, new session, refresh, and thinking toggle.
  * Rendered in the Header when on the Chat page.
  */
-import { RefreshCw, Brain, ChevronDown, Plus } from 'lucide-react';
+import { RefreshCw, Brain } from 'lucide-react';
 import { Button } from '@/components/ui/button';
 import { Tooltip, TooltipContent, TooltipTrigger } from '@/components/ui/tooltip';
 import { useChatStore } from '@/stores/chat';
@@ -11,65 +11,14 @@ import { cn } from '@/lib/utils';
 import { useTranslation } from 'react-i18next';
 
 export function ChatToolbar() {
-  const sessions = useChatStore((s) => s.sessions);
-  const currentSessionKey = useChatStore((s) => s.currentSessionKey);
-  const switchSession = useChatStore((s) => s.switchSession);
-  const newSession = useChatStore((s) => s.newSession);
   const refresh = useChatStore((s) => s.refresh);
   const loading = useChatStore((s) => s.loading);
   const showThinking = useChatStore((s) => s.showThinking);
   const toggleThinking = useChatStore((s) => s.toggleThinking);
   const { t } = useTranslation('chat');
 
-  const handleSessionChange = (e: React.ChangeEvent<HTMLSelectElement>) => {
-    switchSession(e.target.value);
-  };
-
   return (
     <div className="flex items-center gap-2">
-      {/* Session Selector */}
-      <div className="relative">
-        <select
-          value={currentSessionKey}
-          onChange={handleSessionChange}
-          className={cn(
-            'appearance-none rounded-md border border-border bg-background px-3 py-1.5 pr-8',
-            'text-sm text-foreground cursor-pointer',
-            'focus:outline-none focus:ring-2 focus:ring-ring',
-          )}
-        >
-          {/* Render all sessions; if currentSessionKey is not in the list, add it */}
-          {!sessions.some((s) => s.key === currentSessionKey) && (
-            <option value={currentSessionKey}>
-              {currentSessionKey}
-            </option>
-          )}
-          {sessions.map((s) => (
-            <option key={s.key} value={s.key}>
-              {s.key}
-            </option>
-          ))}
-        </select>
-        <ChevronDown className="absolute right-2 top-1/2 -translate-y-1/2 h-3.5 w-3.5 text-muted-foreground pointer-events-none" />
-      </div>
-
-      {/* New Session */}
-      <Tooltip>
-        <TooltipTrigger asChild>
-          <Button
-            variant="ghost"
-            size="icon"
-            className="h-8 w-8"
-            onClick={newSession}
-          >
-            <Plus className="h-4 w-4" />
-          </Button>
-        </TooltipTrigger>
-        <TooltipContent>
-          <p>{t('toolbar.newSession')}</p>
-        </TooltipContent>
-      </Tooltip>
-
       {/* Refresh */}
       <Tooltip>
         <TooltipTrigger asChild>