I would make sure to protect the idea. In France there is a old fashioned way to have a proof that you got the idea first : you can send a letter describing yo

I would make sure to protect the idea. In France there is a old fashioned way to have a proof that you got the idea first : you can send a letter describing your idea to a specific state agency (INPI https://www.inpi.fr/fr/proteger-vos-creations/lenveloppe-soleau/enveloppe-soleau https://www.inpi.fr/fr/proteger-vos-creations/lenveloppe-sol... ). You may have something similar or better in California.