feat: add the disks and cache cards

disks draws a ring per filesystem from the df sample, with the NFS
server address read from the device field and a labelled-bar fallback
when the rings would be too small to read. cache shows the ~/.cache
total and its four largest children from the du sample.

card.ring now resets the cairo path first: a preceding card.text()
leaves a current point, and cairo_arc() joins to it with a straight
line, so the disks rings were drawn with stray chords. The ring
primitive had no caller until now, which is why it went unnoticed.

0 files changed, 0 insertions, 0 deletions