Every move fired StateChangedEvent -> sync_cards, which rebuilt the full
visual for all 52 cards: despawning and respawning every child entity
(drop-shadow, border frame, and on Android a Text2d corner label needing
a glyph re-layout) even for the ~50 cards that did not move. That ~250
entity despawn/spawns plus 52 text re-layouts in a single frame spiked
the StateChangedEvent frame and stuttered the slide animation on
high-resolution devices (reported on a Galaxy Fold 7).
Add a CardChildrenKey component capturing the only inputs the child
entities depend on (face_up, card_size, color_blind, high_contrast).
update_card_entity now rebuilds children only when that key changes (a
flip, resize/fold, or accessibility toggle); a position-only move just
updates the Transform. The Sprite is still refreshed every sync (a cheap
handle swap), so theme/card-back image changes need no child rebuild.
Adds a regression test asserting an appearance-neutral StateChangedEvent
no longer despawns/respawns card label children.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
funman300