Add mocker completion script and update dotfiles configuration

dotfiles/config/zsh/completions/_mocker

@@ -0,0 +1,18 @@
+#compdef mocker
+
+#
+# {{@@ header() @@}}
+#
+
+# Load the completion generated by Mocker itself on first use. Keeping this as
+# a small shim means the available commands and flags always match the installed
+# Mocker version without adding its completion-generation cost to shell startup.
+_mocker() {
+  local completion_script
+
+  completion_script="$(command mocker --generate-completion-script zsh 2>/dev/null)" || return 1
+  [[ -n "${completion_script}" ]] || return 1
+
+  eval "${completion_script}"
+  _mocker "$@"
+}