zsh: move ZSHRC_FUNCTIONS var to functions file

zsh/zsh-functions.zsh

@@ -1,3 +1,5 @@
+ZSHRC_FUNCTIONS="$ZSH_CONFIG/zsh-functions.zsh"
+
 use_dev_branch(){
   mkdir -p "$ZSH_CONFIG"
   echo "dev" > "$ZSH_CONFIG/branch"

zsh/zshrc

@@ -15,8 +15,7 @@ export ZSHRC_BOOTSTRAP="$ZSH_CONFIG/.bootstrapped"
 [[ -d "$HOME/AppImages" ]] && path+=("$HOME/AppImages")
 [[ -d "$HOME/.opencode/bin" ]] && path+=("$HOME/.opencode/bin")
 
-ZSHRC_FUNCTIONS="$ZSH_CONFIG/zsh-functions.zsh"
-source "$ZSHRC_FUNCTIONS"
+source "$ZSH_CONFIG/zsh-functions.zsh"
 
 # Bootstrap: installs missing CLI tools and oh-my-zsh plugins across distros.
 if [[ ! -f "$ZSHRC_BOOTSTRAP" || "$(cat "$ZSHRC_BOOTSTRAP" 2>/dev/null)" != "$ZSHRC_BOOTSTRAP_VERSION" || "$BOOTSTRAP" == "true" ]]; then