Private
Clamp a stack count to upper bound (maxStacks) only, preserving negative values if present. Used by addStack outcome to maintain its original behavior of not enforcing a lower bound.
Proposed stack count
Maximum stacks (null = no upper bound)
Clamped value in [current, max]
Clamp a stack count to upper bound (maxStacks) only, preserving negative values if present. Used by addStack outcome to maintain its original behavior of not enforcing a lower bound.