Fix quoting for annotations. For example, this should now work:
% bundle="zsh-users/zsh-history-substring-search pre:'echo hello \$world' post:'echo \"goodbye \$world\"'"
% antidote bundle $bundle
echo hello $world
fpath+=( $HOME/Library/Caches/antidote/zsh-users/zsh-history-substring-search )
source $HOME/Library/Caches/antidote/zsh-users/zsh-history-substring-search/zsh-history-substring-search.plugin.zsh
echo "goodbye $world"