test: importing the RTC copy E2E script must not change the environment (credential test isolation)

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_rtc_copy_write_guard.py

@@ -9,10 +9,13 @@ ROOT = Path(__file__).resolve().parents[1]
 
 
 def _load():
+    import os
+    before = dict(os.environ)
     sys.path.insert(0, str(ROOT / "scripts")); sys.path.insert(0, str(ROOT / "agent" / "src"))
     spec = importlib.util.spec_from_file_location("rtc_copy_write_e2e", ROOT / "scripts" / "rtc_copy_write_e2e.py")
     module = importlib.util.module_from_spec(spec)
     spec.loader.exec_module(module)
+    assert dict(os.environ) == before, "importing the E2E script must not change the environment"
     return module