Figure out `onCollide` in `volume.js`

onCollide is called once at runtime and is always true. Not entirely sure what the code should be doing - I believe we always want it to be true anyways? That would mean we can just delete the variable nd any associated logic, otherwise fix the event listener

Start in volume.js by tracing where onCollide is defined, called, and connected to the event listener. Determine whether the listener should always report true; done means either removing the unused variable and associated logic or correcting the listener so collision behavior matches the intended result, then verify it at runtime.

Written by the indexing model from the issue text.