The pure, no-IO editor core can't persist or push, so `handle()` now
returns an `Effect` (None/Save/Publish) that the firmware actions. `:w`
signals Save, `:sync` signals Publish (save then git push); `:wq`/`:x`
alias Save with vim's "quit" half dropped, and the `:q` family stays
absent — an always-on appliance has nothing to quit to. `:fmt` remains
in-core and yields no effect.
The main loop keeps the batch's last effect and matches on it. Actual
SD-write and git-push are the v0.1 gate and still stubbed as log lines.
da23b95cfd