This looks great, and feels great (and sounds great). Makes me wanna make 3d game, okay, some day..
At first i was confused because no key worked for Grab, maybe add controls hint like Icon of the button (mabe with Hold text). Love the shaders and controls. As far as i know, you can't force fullscreen in browser, so the click-to-enter-fullscreen seems to be the best (and only) option. I use fullscrenn this way too for my games. And i never saw auto-fullscreen. You can launch in almost fullscreen with right settings, and eneble fullscreen with F11, this way it does not exit it when pressing Esc. But you asking player to press F11, that is a drawback of that way.
Anyway, great stuff!