fix(tui): restructure Sidebar component to be scrollable (#3946)

packages/opencode/src/cli/cmd/tui/routes/session/sidebar.tsx

@@ -40,7 +40,8 @@ export function Sidebar(props: { sessionID: string }) {
 
   return (
     <Show when={session()}>
-      <box flexShrink={0} gap={1} width={40}>
+      <scrollbox width={40}>
+        <box flexShrink={0} gap={1} paddingRight={1}>
           <box>
             <text fg={theme.text}>
               <b>{session().title}</b>
@@ -170,6 +171,7 @@ export function Sidebar(props: { sessionID: string }) {
             </box>
           </Show>
         </box>
+      </scrollbox>
     </Show>
   )
 }