Add execution graph to chat history (#776)

src/components/layout/MainLayout.tsx

@@ -13,9 +13,9 @@ export function MainLayout() {
       <TitleBar />
 
       {/* Below the title bar: sidebar + content */}
-      <div className="flex flex-1 overflow-hidden">
+      <div className="flex min-h-0 flex-1 overflow-hidden">
         <Sidebar />
-        <main data-testid="main-content" className="flex-1 overflow-auto p-6">
+        <main data-testid="main-content" className="min-h-0 flex-1 overflow-auto p-6">
           <Outlet />
         </main>
       </div>

src/components/layout/Sidebar.tsx

@@ -219,7 +219,7 @@ export function Sidebar() {
     <aside
       data-testid="sidebar"
       className={cn(
-        'flex shrink-0 flex-col border-r bg-[#eae8e1]/60 dark:bg-background transition-all duration-300',
+        'flex min-h-0 shrink-0 flex-col overflow-hidden border-r bg-[#eae8e1]/60 dark:bg-background transition-all duration-300',
         sidebarCollapsed ? 'w-16' : 'w-64'
       )}
     >
@@ -279,7 +279,7 @@ export function Sidebar() {
 
       {/* Session list — below Settings, only when expanded */}
       {!sidebarCollapsed && sessions.length > 0 && (
-        <div className="flex-1 overflow-y-auto overflow-x-hidden px-2 mt-4 space-y-0.5 pb-2">
+        <div className="mt-4 flex-1 overflow-y-auto overflow-x-hidden px-2 pb-2 space-y-0.5">
           {sessionBuckets.map((bucket) => (
             bucket.sessions.length > 0 ? (
               <div key={bucket.key} className="pt-2">