ci: Add root conftest.py to fix coverage under pytest

Isolates whether a root conftest.py (which puts the repo root on
sys.path early, before coverage resolves --cov=injector) makes plain
`pytest --cov=injector` measure the working-tree copy the tests run.
DIAG print is temporary.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: davidparsson

.github/workflows/ci.yml

@@ -34,17 +34,7 @@ jobs:
         pip install .
     - name: Run tests
       run: |
-        site_packages=$(python -c 'import sysconfig; print(sysconfig.get_path("purelib"))')
-        # --- TEMP DIAGNOSTICS ---
-        echo "DIAG PWD=$PWD"
-        echo "DIAG site_packages=$site_packages"
-        printf 'import sys\ndef pytest_collection_finish(session):\n    m = sys.modules.get("injector")\n    print("DIAG executed-injector:", getattr(m, "__file__", m))\n    print("DIAG sys.path head:", sys.path[:6])\n' > conftest.py
-        # --- END TEMP ---
-        pytest -vv --cov="$PWD/injector" --cov="$site_packages/injector" --cov-branch --cov-report html --cov-report term || true
-        # --- TEMP DIAGNOSTICS ---
-        python -c "import coverage; d=coverage.CoverageData(); d.read(); print('DIAG measured:', list(d.measured_files()))" || true
-        rm -f conftest.py
-        # --- END TEMP ---
+        pytest -vv --cov=injector --cov-branch --cov-report html --cov-report term
         if which mypy; then mypy injector ; fi
         if which black; then black --check . ; fi
         check-manifest

conftest.py

@@ -0,0 +1,6 @@
+import sys
+
+
+def pytest_collection_finish(session):
+    m = sys.modules.get("injector")
+    print("DIAG executed-injector:", getattr(m, "__file__", m))