v0.3.0

add plugins: archive, cdm, cron, diff, find, ssh

- archive: tar/zip/7z create, extract, list with preview
- cdm: mkdir+cd with shell-function init (proto cdm init)
- cron: humanized crontab with next-run predictions and validation
- diff: side-by-side/unified file diff + recursive dir diff
- find: rg/fd/find backends with interactive fuzzy picker
- ssh: host manager parsing ~/.ssh/config

fixes:
- shared::which: scan PATH instead of shelling out to which
- img: prefer kitty icat, fall back to chafa/viu/jp2a ANSI preview
- font: install creates ~/.local/share/fonts and runs fc-cache