input: keyboard

I think it should be mapped to canvas keyboard events (the same canvas used for framebuffer?) I think it should go in `/dev/input/keyboard` or `/dev/input/eventX`

The issue mentions canvas keyboard events, the framebuffer canvas, and the paths /dev/input/keyboard or /dev/input/eventX, but no repository files or tests. First locate the existing framebuffer, canvas, and input entry points, then determine which input path the project uses; done means keyboard input is mapped consistently and covered by an appropriate test or documented verification.

Written by the indexing model from the issue text.