Warrior Spirits

The developers describe how their game uses AI generated content like this:

This game was developed solo, using generative AI tools to assist with parts of the art and the music.

Required on Steam store pages since 2024. It covers content that ships in the game, on its store page or in its marketing — Valve does not require a disclosure for AI tools used during development, so this says nothing either way about how the game was made. Check it on Steam.