test(github): clear GITHUB_TOKEN env in test_throws_when_no_auth

TestGitHubAdapterConstructor.test_throws_when_no_auth expected
ValidationError on auth-less construction, but the GitHubAdapter
constructor's env-fallback path silently satisfied auth from a
GITHUB_TOKEN set by CI / dev shell — so the test failed wherever
GITHUB_TOKEN was set in the environment.

The duplicate test at line 827 in this same file already does the
env-var cleanup correctly. Apply the same pattern to line 190 so the
suite is fully green for the 0.4.27 release: pop GITHUB_TOKEN /
GITHUB_APP_ID / GITHUB_PRIVATE_KEY before the assert, restore them in
finally.

Author: claude

tests/test_github_webhook.py

@@ -188,14 +188,27 @@ def test_create_single_tenant_app(self):
         assert a.is_multi_tenant is False
 
     def test_throws_when_no_auth(self):
-        with pytest.raises(ValidationError, match="Authentication"):
-            GitHubAdapter(
-                {
-                    "webhook_secret": "secret",
-                    "user_name": "bot",
-                    "logger": ConsoleLogger("error"),
-                }
-            )
+        # Clear env vars so the constructor's env-fallback path can't
+        # silently satisfy auth from a GITHUB_TOKEN injected by CI / dev shell.
+        old_token = os.environ.pop("GITHUB_TOKEN", None)
+        old_app = os.environ.pop("GITHUB_APP_ID", None)
+        old_key = os.environ.pop("GITHUB_PRIVATE_KEY", None)
+        try:
+            with pytest.raises(ValidationError, match="Authentication"):
+                GitHubAdapter(
+                    {
+                        "webhook_secret": "secret",
+                        "user_name": "bot",
+                        "logger": ConsoleLogger("error"),
+                    }
+                )
+        finally:
+            if old_token is not None:
+                os.environ["GITHUB_TOKEN"] = old_token
+            if old_app is not None:
+                os.environ["GITHUB_APP_ID"] = old_app
+            if old_key is not None:
+                os.environ["GITHUB_PRIVATE_KEY"] = old_key
 
     def test_bot_user_id_when_set(self):
         a = _make_adapter(bot_user_id=42)