Tooltip works poorly with the OutputContainer dialog

[syimyuzya]

f8d3d3e made the OutputContainer a <dialog>, but broke the Tooltip's Z-order. 5b15b1a kinda fixed the Z-order, but introduced new problems:

• Tooltip's position is incorrect when the OutputContainer is scrolled (temporarily fixed™️ with some hack)
• Attaching the Tooltip's <div> (which is a separate React root) to a parent node managed by another React root is probably a bad idea, and may further cause some unexpected behaviors.