Spells whose cost is reduced to 0 are not prompted to be played, unlike other free spells.

Steps to reproduce:
- Play effects which reduce the cost of artifacts like [[Etherium Sculptor]] or [[Foundry Inspector]]
- Play an artifact whose cost has been reduced to 0 mana
- Expect a prompt, instead it just directly plays.

Start by reproducing the artifact-cost reduction steps with Etherium Sculptor or Foundry Inspector and confirm that a zero-cost artifact plays without a prompt. Trace the relevant spell-playing behavior, then verify that reduced-to-zero spells receive the same prompt as other free spells.

Written by the indexing model from the issue text.