doHCFILES.yml: replace 5 separate checkout steps with a single
checkout using submodules:true; remove now-redundant .git cleanup step.
buildLoadup.yml: add submodules:true to Checkout Medley; remove
separate Checkout Notecards + tar steps (notecards.tgz was already
commented out of the release push).
make-gh-pages.md: replace manual clone+copy instructions with
git clone --recurse-submodules; remove rm -rf of submodule dirs.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>