✅ Regression state immutability

Category	Regression
Status	Passing
Test	tests/test_abilities_actions.py::test_regression_state_immutability

execute_ability must return a new GameState without mutating input.

Preconditions

• P1 has 5 AP, Sabnock READIED, Duban READIED with 0 damage

Action

• execute_ability(state, sabnock, ...)

result = execute_ability(state, sabnock_on_field, ability_idx=0, targets=[duban_on_field])

Expected Postconditions

• Original state.players[P1].ap is still 5 (not mutated)

• Original state has no status effects (not mutated)

• result is a different object from state

Assertions

assert state.players[Side.PLAYER_1].ap == original_ap
    assert len(state.status_effects) == original_effects_count
    assert result is not state