zsh: escape cdpath entries

Zsh cdpath is an array. Rendering entries by joining on spaces breaks paths containing spaces, glob characters, or other shell syntax.

Use the shared shell array formatter so each configured cdpath entry is emitted as a quoted array element.

tests/modules/programs/zsh/zshrc-content-priorities.nix

@@ -3,6 +3,12 @@
   programs.zsh = {
     enable = true;
 
+    cdpath = [
+      "$HOME/projects"
+      "/tmp/with space"
+      "/tmp/with[glob]"
+    ];
+
     initContent = lib.mkMerge [
       (lib.mkBefore ''
         # High priority (mkBefore)
@@ -34,6 +40,8 @@
           echo "High priority content"
 
           typeset -U path cdpath fpath manpath
+          cdpath+=("$HOME/projects" "/tmp/with space" "/tmp/with[glob]")
+
           for profile in ''${(z)NIX_PROFILES}; do
             fpath+=($profile/share/zsh/site-functions $profile/share/zsh/$ZSH_VERSION/functions $profile/share/zsh/vendor-completions)
           done