codexloop testing

tests/domain/            # pure unit + Hypothesis
tests/application/       # fakes for every port (application/interfaces/)
tests/infrastructure/    # adapters
tests/shim/              # fake_codex.py + fake_appserver.py — executable fakes
tests/live/              # marker: live — real OpenAI account, opt-in

pytest                 # skips live (default -m "not live and not system")
pytest -m system       # real FS/git + scripted agent
pytest -m live         # needs OPENAI_API_KEY

• Fakes over mocks. Implement the Protocol; mypy --strict checks it.
• Executable shims. fake_codex.py and fake_appserver.py in
  tests/shim/ are genuine executables driven by env vars — the only such
  fakes in the fleet. They let you script exact output sequences without
  touching the OpenAI SDK.
• No time.sleep in tests. FakeClock / FakeSleeper.
• Hypothesis for numeric / time-based invariants.
• # pragma: no cover needs a reason.
• 100% branch coverage per layer, enforced by gate:

  pytest -q --cov=codexloop.domain --cov-fail-under=100
  pytest -q --cov=codexloop.application --cov-fail-under=100
  pytest -q --cov=codexloop.infrastructure --cov-fail-under=100
  pytest -q --cov=codexloop.cli --cov-fail-under=100