fix: resolve 8 test failures from missing requests stub and wrong python path

- Add `requests` to conftest.py module stubs so patch("requests.post") works
  in reward scoring tests without the package installed
- Use sys.executable instead of bare "python" in git safety tests so the
  subprocess finds pytest from the venv rather than system python

https://claude.ai/code/session_012Ye9nyFEiw2QQfx4bZeDmn

tests/conftest.py

@@ -33,6 +33,9 @@ for _mod in [
     # pyzbar is optional (for QR code invite detection)
     "pyzbar",
     "pyzbar.pyzbar",
+    # requests is optional — used by reward scoring (swarm.learner) to call
+    # Ollama directly; stub so patch("requests.post") works in tests.
+    "requests",
 ]:
     sys.modules.setdefault(_mod, MagicMock())