fix: derive non-marker children synchronously to avoid stale map layers

[tim-baecker]

Problem

Non-marker children (Polyline, Overlay, etc.) were stored in React state and only updated in useEffect after splitting propsChildren. When those children were removed from props (e.g. toggling map layers off), native map views could stay on screen even though React no longer rendered them.

Solution

Derive non-marker children synchronously with useMemo from propsChildren (same rules as before: all children when clusteringEnabled is false, otherwise everything that is not a Marker). The clustering useEffect only builds rawData from markers.

Notes

• Behavior for clustering and spider lines is unchanged; only the source of truth for “other” children is fixed.
• Tested in an app using many polylines + toggling visibility.