refactor code and add fallback prompt to zsh

profiles/base/.bash/conf.d/04-env.bash

@@ -1,5 +1,5 @@
 # Set environment variables
-if command -v nvim &> /dev/null; then
+if command -v nvim >/dev/null 2>&1; then
     export EDITOR="nvim"
 else
     export EDITOR="vim"
@@ -21,7 +21,7 @@ export GPGKEY="4A45503BBE575E3D4DAF28E27264AFFDC98D52BB"
 
 # gpg-agent
 unset SSH_AGENT_PID
-if [ "${gnupg_SSH_AUTH_SOCK_by:-0}" -ne $$ ]; then
-    SSH_AUTH_SOCK="$(gpgconf --list-dirs agent-ssh-socket 2>/dev/null)"
+if [[ "${gnupg_SSH_AUTH_SOCK_by:-0}" -ne "$$" ]]; then
+    SSH_AUTH_SOCK=$(gpgconf --list-dirs agent-ssh-socket 2>/dev/null)
     export SSH_AUTH_SOCK
 fi