fix: prune exiting digit slot when its fade animation is interrupted

[saileshbro]

The bug

useSlotOpacity gates onExitComplete on finished === true:

(finished) => {
  "worklet";
  if (finished && onExitComplete && exitKey) {
    runOnJS(onExitComplete)(exitKey);
  }
},

An interrupted withTiming reports finished: false. useLayoutDiff keeps a key in exitingRef until onExitComplete fires for it, so when the fade is interrupted the key is never removed — the exiting glyph stays mounted on top of the live one indefinitely.

Reproducing

Anything that cancels the exit fade mid-flight:

• change the value twice in quick succession, so a slot that is mid-exit is re-diffed
• any re-render/teardown that cancels the animation while it is running — in our case tapping a card that pushes a formSheet over the screen while the digits were still rolling

Result: every slot that was mid-exit is left permanently doubled — the hero number, a secondary line and a percentage all rendering two superimposed digit stacks (2,238 over 2,276, and so on). It does not recover, because nothing else prunes exitingRef.

The fix

Report completion regardless of finished.

This is safe: useLayoutDiff already deletes any key present in the current layout during its diff —

for (const key of currentKeys) {
  exitingRef.current.delete(key);
}

— so a slot that has re-entered is never removed by this path. The callback only ever cleans up a slot that stopped animating, for whatever reason.

Notes

• Verified on iOS (RN 0.83, Reanimated 4.5, native renderer) — the doubling was reproducible on demand before, and is gone after.
• Added a patch changeset.
• Happy to adjust the comment wording or split it if you would prefer a narrower guard (e.g. tracking cancellation explicitly rather than pruning on any non-finish).

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