Remove the constant time-based rotation, in favor of mouselook.  Add a pitch and yaw global angle and use them in a mousemove handler that updates the view mat4.  Set up pointerlock (via experimental apis; whee), turning that handler on and off when pointerlock is obtained and lost.  Delete all the code for constant-speed rotation.  Still need to provide a way to *move* the camera, instead of just rotating it, but this is enough for now.