keypress-listener.js & other Aframe event listeners

Event listeners for `window`, `document`, etc should be attached to `a-scene` not any individual entity.

Make sure the listeners update the volume immediately - force `volume.js` update function to run

Do we even need `keypress-listener.js`? Is turning the clipping on and off separately from the controls something the user desires?

Start by reading keypress-listener.js and volume.js, then trace where event listeners are attached to individual entities versus a-scene. Check whether the listeners can trigger volume.js updates immediately and clarify whether keypress-listener.js is still needed; done means the listener placement and clipping behavior match the intended controls.

Written by the indexing model from the issue text.