Add support for ssh-agent

[varlogtim]

So... we need to add this to a make file for the general system

ssh-add -l
If the agent is not running (error persists), start it:

eval "$(ssh-agent -s)"

Then retry ssh-add -l

For automatic startup on Arch with Sway, add to ~/.bashrc:

if ! pgrep -u "$USER" ssh-agent > /dev/null; then
ssh-agent -t 1h > "$XDG_RUNTIME_DIR/ssh-agent.env"
fi
if [ ! -f "$SSH_AUTH_SOCK" ]; then
source "$XDG_RUNTIME_DIR/ssh-agent.env" >/dev/null
fi

Source the file or restart shell.

Probably do this:
Alternatively, use systemd (openssh >=9.4p1-3): systemctl --user enable --now ssh-agent.service

Docs: https://wiki.archlinux.org/title/SSH_keys#SSH_agents

---

OK, the following is actually better:

As a part of bashrc get-deps (or something)
systemctl --user enable ssh-agent.service

Then:
export SSH_AUTH_SOCK="$XDG_RUNTIME_DIR/ssh-agent.socket"