Bidet sprayer install and toilet leak at supply line
Probably what happened is the black plastic nut on the supply line cracked. It looks pretty old and might have been over-tightened when you hooked it up to the bidet. You said the supply line can't be replaced - but it can. The supply line looks like pex and runs straight out of the wall. Is there a shutoff for it? Or did you have to turn off the water at the main?
I don't know how handy you are but if it's pex or something similar and there's no shutoff you should install one at the wall. You can get a 1/4 turn shutoff with a pex connection at a home center store. Purchase a new flexible supply line for a toilet so it will have the correct size fitting to attach to either the tank or the bidet.