chore: preserve 'pytype' artifacts during synth (#90)

* chore: use '.pytype' vs. 'pytype_output' for pytype cache

* chore: add snippet-bot to CI (via synth)

* chore: drop obsolete warning about editable installs

* chore: add secrets manager, docs-presubmit to CI (via synth)

* chore: manual synth

Closes: #66.
Closes: #56.
22 files changed