Refterm v2: Fast GPU Terminal Rendering and Unicode Handling

HN points to it as proof that a small, straightforward renderer can beat Windows Terminal on speed and memory, whenever software slowness comes up.

Casey Muratori follows up his refterm proof-of-concept, a GPU-based terminal renderer, with a second part covering memory usage, glyph sizing and correct Unicode and VT handling. It is built to show that a terminal can be fast and correct without heroic effort.