Documented in :file:`AGENTS.md` that the coverage report covers
``tests/`` as well as ``aiohttp/`` (so unreachable defensive
``raise`` guards in patched stubs and one-sided cleanup branches
in tests will surface as uncovered on the codecov patch report),
and that the docs spell check (``make doc-spelling``) is a hard
CI gate that reads every ``CHANGES/*.rst`` fragment and should be
run locally before pushing
-- by :user:`bdraco`.
