Migrate the Chef repo to Cinc Workstation

Cinc Workstation replaces Chef Workstation for driving knife-zero and
Test Kitchen; nodes run (or are moving to) Cinc Client.

- Pin .ruby-version to cinc-workstation
- Move knife config from .chef/ to .cinc/ (Cinc's USER_CONF_DIR) and
  update .gitignore, README, AGENTS and docs accordingly. On-node config
  now lives in /etc/cinc
- Drop the Gemfile/Gemfile.lock; install knife-zero into Cinc
  Workstation's user gem dir with `cinc gem install knife-zero`
- README: rewrite setup/usage for Cinc Workstation
- scripts/postgresql/switch_primary.sh: drop `bundle exec`

scripts/postgresql/switch_primary.sh

@@ -9,14 +9,14 @@ fi
 
 old_primary_hostname=$1
 new_primary_hostname=$2
-new_primary_ip=`bundle exec knife node show $new_primary_hostname -a knife_zero.host | grep -E "([0-9]{1,3}[\.]){3}[0-9]{1,3}" -o`
+new_primary_ip=`knife node show $new_primary_hostname -a knife_zero.host | grep -E "([0-9]{1,3}[\.]){3}[0-9]{1,3}" -o`
 
 echo "Switching primary to $new_primary_hostname ($new_primary_ip)"
-bundle exec knife ssh name:$new_primary_hostname -a knife_zero.host "sudo su - postgres -c '/usr/lib/postgresql/12/bin/pg_ctl promote -D /var/lib/postgresql/12/main'"
+knife ssh name:$new_primary_hostname -a knife_zero.host "sudo su - postgres -c '/usr/lib/postgresql/12/bin/pg_ctl promote -D /var/lib/postgresql/12/main'"
 echo "Stopping postgresql on $old_primary_hostname"
-bundle exec knife ssh name:$old_primary_hostname -a knife_zero.host "sudo systemctl stop postgresql@12-main.service"
+knife ssh name:$old_primary_hostname -a knife_zero.host "sudo systemctl stop postgresql@12-main.service"
 echo "Replacing pg.kosmos.local host entries with $new_primary_ip"
-bundle exec knife ssh roles:postgresql_client -a knife_zero.host "sudo sed -r \"s/^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+\s(pg.kosmos.local)/$new_primary_ip\t\1/\" -i /etc/hosts"
+knife ssh roles:postgresql_client -a knife_zero.host "sudo sed -r \"s/^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+\s(pg.kosmos.local)/$new_primary_ip\t\1/\" -i /etc/hosts"
 
 # TODO
 # 1. Change roles in node configs