fix(shell): use single ~/.config/zsh/local.zsh for machine local

Replace the local/ directory of split env/login/interactive files with
one always-on local.zsh sourced from .zshenv. Deploy migrates old
fragments and never overwrites local.zsh.

.zprofile

@@ -1,5 +1,5 @@
 # easyzsh stub: login shells only. Not the PATH source of truth (see env/00-path.zsh).
-# Put OS/vendor login hooks in ~/.config/zsh/local/login.local.zsh.
+# Machine-local overrides live in ~/.config/zsh/local.zsh (loaded from .zshenv).
 EASYZSH_HOME="${XDG_CONFIG_HOME:-$HOME/.config}/zsh"
 
 if [[ -d "$EASYZSH_HOME/login" ]]; then
@@ -9,8 +9,3 @@ if [[ -d "$EASYZSH_HOME/login" ]]; then
   done
   unset _easyzsh_f
 fi
-
-if [[ -f "$EASYZSH_HOME/local/login.local.zsh" ]]; then
-  # shellcheck disable=SC1090
-  . "$EASYZSH_HOME/local/login.local.zsh"
-fi