fix(mobile): preserve chat rows when toggling commands

apps/mobile/src/features/threads/ThreadFeed.tsx

@@ -210,6 +210,7 @@ function formatMessageTime(input: string): string {
 // text fits at the current font settings. Larger accessibility text is measured.
 const TURN_FOLD_HEIGHT = 42; // min-h-11 (38.5) + mb-1 (3.5), with the mobile 14px rem
 const THREAD_FEED_LAYOUT_TRANSITION = LinearTransition.duration(THREAD_DISCLOSURE_TRANSITION_MS);
+const THREAD_FEED_IMMEDIATE_TRANSITION = LinearTransition.duration(0);
 // Tailwind spacing on the mobile 14px rem: px-3.5 on the user bubble, px-1 on
 // assistant rows. Images size their frame from these before their own layout.
 const USER_BUBBLE_HORIZONTAL_PADDING = 3.5 * 3.5;
@@ -2863,8 +2864,13 @@ export const ThreadFeed = memo(function ThreadFeed(props: ThreadFeedProps) {
               entry.type === "message" ? `message:${entry.message.role}` : entry.type
             }
             getFixedItemSize={getFixedItemSize}
+            // LegendList swaps its position and size component types when this
+            // becomes undefined, remounting the feed and replaying row entrances.
+            // Keep those containers mounted while ordinary updates stay immediate.
             itemLayoutAnimation={
-              disclosureToggleSettling ? THREAD_FEED_LAYOUT_TRANSITION : undefined
+              disclosureToggleSettling
+                ? THREAD_FEED_LAYOUT_TRANSITION
+                : THREAD_FEED_IMMEDIATE_TRANSITION
             }
             onItemSizeChanged={handleItemSizeChanged}
             // Measure rows well before they scroll into view so estimate→actual