fix(mobile): forget queued-row heights for messages that left the queue

The queued list cached each row's height by message id for the life of the
chat, so a long conversation kept one entry per message ever queued and a
requeued id could place a failed row by the height it left with. Keep heights
only for queued ids, and drop a layout a departed row reports late.

mobile/src/session/native-chat/input/MobileNativeChatQueuedMessages.test.tsx

@@ -431,6 +431,60 @@ describe('MobileNativeChatQueuedMessages', () => {
     }
   })
 
+  it('places a failed row by the height a returning message lays out at, not the one it left with', async () => {
+    const scrollTo = vi.fn()
+    const mounted = create(createElement('View'), {
+      createNodeMock: (node) =>
+        node.type === 'ScrollView'
+          ? { scrollTo, scrollToEnd: vi.fn(), flashScrollIndicators: vi.fn() }
+          : null
+    })
+    renderer = mounted
+    // Rows render in queue order.
+    const layRow = async (index: number, height: number) => {
+      const row = rows(mounted)[index]!
+      await act(async () => row.props.onLayout({ nativeEvent: { layout: { height } } }))
+    }
+    await act(async () =>
+      mounted.update(
+        element({
+          cards: [card({ messageId: 'a' }), card({ messageId: 'b' }), card({ messageId: 'c' })]
+        })
+      )
+    )
+    const scroll = mounted.root.find((node) => String(node.type) === 'ScrollView')
+    await act(async () => {
+      scroll.props.onLayout({ nativeEvent: { layout: { height: 100 } } })
+      scroll.props.onContentSizeChange(0, 300)
+    })
+    // b leaves tall (an open editor or expanded text), then comes back as a plain 60pt row.
+    await layRow(0, 60)
+    await layRow(1, 180)
+    await layRow(2, 60)
+    await act(async () =>
+      mounted.update(element({ cards: [card({ messageId: 'a' }), card({ messageId: 'c' })] }))
+    )
+    scrollTo.mockClear()
+    await act(async () =>
+      mounted.update(
+        element({
+          cards: [
+            card({ messageId: 'a' }),
+            card({ messageId: 'b' }),
+            card({ messageId: 'c', needsAttention: true, caption: "Couldn't send" })
+          ]
+        })
+      )
+    )
+    // The failed row reports before b does; b's old height must not place it.
+    await layRow(2, 60)
+    expect(scrollTo).not.toHaveBeenCalled()
+    await layRow(1, 60)
+    // c spans 120–180 of a 100pt list: the nearest scroll that shows it, clear of the edge fade.
+    expect(scrollTo).toHaveBeenCalledTimes(1)
+    expect(scrollTo).toHaveBeenCalledWith({ y: 96, animated: false })
+  })
+
   it('scrolls to a failure the list mounts open for, and settles when no row lays out again', async () => {
     vi.useFakeTimers()
     try {

mobile/src/session/native-chat/input/mobile-queued-row-frame.ts

@@ -31,6 +31,10 @@ export const QUEUED_ROW_SHOW_SETTLE_MS = 300
 
 type ShowRow = (row: LayoutRectangle) => void
 
+// Message ids cannot contain NUL.
+const ID_SEPARATOR = '\u0000'
+const NO_IDS: ReadonlySet<string> = new Set()
+
 /**
  * Scrolls the queue to one row (a failure that opened the list) once that row has laid out again.
  * A row whose height never changes reports no layout, so the request settles shortly after either way.
@@ -51,6 +55,20 @@ export function useQueuedRowShow(
   useLayoutEffect(() => {
     order.current = messageIds
   })
+  // Only queued rows keep a height, so a long conversation holds none for messages that left, and
+  // an id that comes back (a requeued draft) waits for its own fresh layout.
+  const liveKey = messageIds.join(ID_SEPARATOR)
+  // Filled before any row lays out: layout effects run before native layout events.
+  const live = useRef(NO_IDS)
+  useLayoutEffect(() => {
+    live.current = new Set(liveKey ? liveKey.split(ID_SEPARATOR) : [])
+    for (const messageId of heights.current.keys()) {
+      if (!live.current.has(messageId)) {
+        heights.current.delete(messageId)
+        fresh.current.delete(messageId)
+      }
+    }
+  }, [liveKey])
   useLayoutEffect(() => {
     fresh.current.clear()
   }, [showId])
@@ -73,6 +91,10 @@ export function useQueuedRowShow(
     height: number,
     show: ShowRow
   ) => {
+    // A row that already left can still report a layout queued before it went.
+    if (!live.current.has(messageId)) {
+      return
+    }
     const { showAll } = list
     shownAll.current = showAll
     heights.current.set(messageId, height)