Fix "Don Thousand/Spell A"

[botist]

Don Thousand/Spell A currently retains the Spell/Trap sent for its cost with Duel.SetTargetCard. This adds that card to the current chain's target group. When the copied operation later calls Duel.GetFirstTarget(), it can receive the sent card in the Graveyard instead of the target selected by the copied effect. As a result, costs are paid but effects such as Raigeki Break and Tribute to The Doomed fail to destroy their target.

This change stores each sent card separately using the activation's unique chain ID. It does not overwrite label state used by copied effects, supports multiple activations in the same chain, and leaves the target group available exclusively to the copied effect.

The target-relation handling now also permits an absent target group, preserving the intended Boss Duel interaction with the no-target Don Thousand/Spell B (Numeron Calling) effect.

Verified with Project Ignis ScriptChecker v1.5 using the current ProjectIgnis/bin ocgcore. Targeted regressions covered both a cost-plus-target destruction-style effect and the original no-target Boss Duel effect.

• I am following the contributing guidelines.
• I am making the changes to modernize the scripts.