I looked something up since my last post (#26). The law firm at the link below says that the British monarch has the power to dissolve Parliament on his own.
That power was evidently restored to the monarch by the Dissolution and Calling of Parliament Act of 2022. However, not every site I checked agrees.
https://www.milnerslaw.co.uk/could-king-charles-iii-dissolve-parliament/
I found the same confusion.