Neo: stop the VirtuosoGrid stack overflow on browse grids (#5824)

/persons-active (and any grid browse) threw "Maximum call stack size
exceeded" from react-virtuoso on load when a card grew after its first
measurement: the action button chunk loads late and adds 36px. VirtuosoGrid
then lays out rows with the new height while its list boundary still has
the old one. With a numeric overscan the visible range depends on the
direction the list last grew, so each pass flipped the direction and the
range alternated between two values until the stack ran out.

UniList (web) now passes overscan as { main, reverse } with equal values,
including a numeric overscan from callers, so the range depends on the
scroll position only and the next pass settles. increaseViewportBy is a
module constant because Virtuoso republishes every prop on each render.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

neo/packages/app/ui/atoms/unilist/index.web.tsx

@@ -49,6 +49,32 @@ function parseHeight(height: unknown): string | undefined {
     return value
 }
 
+/**
+ * Pixels rendered past each edge of the viewport, so window scroll never shows
+ * a blank band on a fast wheel. A module constant: Virtuoso republishes every
+ * prop on each render, and a new object makes it recompute the visible range.
+ */
+const INCREASE_VIEWPORT_BY = { top: 3000, bottom: 3000 }
+
+type Overscan = { main: number; reverse: number }
+
+/**
+ * Virtuoso `overscan` with the same value on both sides. A bare number only
+ * extends the list in the direction it last grew, so the visible range depends
+ * on that direction. When a grid item is re-measured (a card's button chunk
+ * loads and the card grows), VirtuosoGrid lays out its rows with the new height
+ * while its list boundary still has the old one; with a one-sided overscan each
+ * pass then flips the direction, the range alternates between two values, and
+ * the recursion ends in "Maximum call stack size exceeded". With equal sides the
+ * range depends on the scroll position only, so the next pass repeats it and
+ * Virtuoso stops there.
+ */
+function overscanBothSides(overscan: unknown, fallback: number): Overscan {
+    if (overscan && typeof overscan === 'object') return overscan as Overscan
+    const px = typeof overscan === 'number' ? overscan : fallback
+    return { main: px, reverse: px }
+}
+
 /** Grid container: rows wrap horizontally. */
 const GridListComponent = forwardRef<HTMLDivElement, HTMLAttributes<HTMLDivElement>>(function GridListComponent({ className, ...props }, ref) {
     return (
@@ -90,10 +116,16 @@ export default function UniList(props: UniListProps) {
         url,
         refreshing,
         onRefresh,
+        overscan: overscanProp,
         ...restProps
     } = props
-    // Anything left over is a Virtuoso prop (overscan, computeItemKey, …).
+    // Anything left over is a Virtuoso prop (computeItemKey, …).
     const rest = omitProps(restProps, [...NATIVE_ONLY_PROPS, ...IGNORED_PROPS])
+    // Notifications are short rows; everything else pre-renders generously.
+    const overscan = useMemo(
+        () => overscanBothSides(overscanProp, unit === 'notifications' ? 100 : 900),
+        [overscanProp, unit]
+    )
 
     const uniRef = useRef<any>(undefined)
     const rows = useMemo(() => dedupeById(rawData), [rawData])
@@ -211,10 +243,8 @@ export default function UniList(props: UniListProps) {
         ref: refer ?? uniRef,
         startReached: onStartReached,
         endReached: onEndReached,
-        // Notifications are short rows; everything else pre-renders generously
-        // so window-scroll never shows a blank band on a fast wheel.
-        overscan: unit === 'notifications' ? 100 : 900,
-        increaseViewportBy: { top: 3000, bottom: 3000 },
+        overscan,
+        increaseViewportBy: INCREASE_VIEWPORT_BY,
         components: {
             ...(isGrid ? { List: GridListComponent, Item: GridItemComponent } : {}),
             Footer: FooterComponent,