When an opponent's card effect forces my unit from one battlefield to a battlefield they control, who gets priority/focus to cast the first action/reaction in the resulting showdown?

Ruling: The player whose unit was forced to move becomes the attacker and gets focus first, because their unit is the one that applied contested status.

Sequence:

• The unit is forced to move to the opponent's controlled battlefield
• This causes the moved unit to apply contested status
• The owner of the moved unit becomes the attacker
• The attacker gets focus and can play the first action spell