style: set Independent Panel sidebar width to a fixed value and default collapsed

src/pages/IndependentPanel/App.jsx

@@ -18,7 +18,7 @@ import Browser from 'webextension-polyfill'
 
 function App() {
   const { t } = useTranslation()
-  const [collapsed, setCollapsed] = useState(false)
+  const [collapsed, setCollapsed] = useState(true)
   const config = useConfig()
   const [sessions, setSessions] = useState([])
   const [sessionId, setSessionId] = useState(null)

src/pages/IndependentPanel/styles.scss

@@ -46,18 +46,21 @@
   .chat-sidebar {
     display: flex;
     flex-direction: column;
+    min-width: 250px;
     width: 250px;
     background-color: var(--theme-color);
-    transition: width 0.3s;
+    transition: width 0.3s, min-width 0.3s;
     padding: 10px;
   }
 
   .chat-sidebar.collapsed {
+    min-width: 60px;
     width: 60px;
   }
 
   .chat-sidebar:hover,
   .chat-sidebar:not(.collapsed) {
+    min-width: 250px;
     width: 250px;
   }