more informative dot, and in samples or seconds, not bytes
release /dev/audio on unpause, just keep playing on prompt
redraw: most redrawing only involves reseting view offsets and blanking bg
drawsamps: fix overshooting bin at the end of a batch and simplify some
use default man target from /sys/src/cmd/mkone
add -f: don't read whole file into memory at startup
split source up to facilitate extension