test(integration): swap bad-auth probe from markets.list to portfolio.balance

markets.list() no longer exercises the auth path — Kalshi began serving
public market data unauthenticated, so a client with bad credentials
gets a 200 back instead of 401/403 and the test "DID NOT RAISE".

Switched to portfolio.balance(), which is account-scoped and always
auth-required. Added a docstring note so future maintainers know why
the endpoint choice matters.

Closes 1 of 11 integration-test failures (#124).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: TexasCoding

tests/integration/test_errors.py

@@ -54,6 +54,11 @@ def test_bad_auth_returns_auth_error(self) -> None:
 
         Uses a throwaway client with a valid RSA key but wrong key_id,
         so signing succeeds but the server rejects the credentials.
+
+        Targets ``portfolio.balance()`` because it is account-scoped and
+        always auth-required. ``markets.list()`` was previously used but
+        Kalshi began serving public market data unauthenticated, so it
+        no longer exercises the auth path.
         """
         dummy_key = rsa.generate_private_key(
             public_exponent=65537, key_size=2048
@@ -68,7 +73,7 @@ def test_bad_auth_returns_auth_error(self) -> None:
 
         try:
             with pytest.raises(KalshiAuthError) as exc_info:
-                client.markets.list(limit=1)
+                client.portfolio.balance()
 
             exc = exc_info.value
             assert exc.status_code in (401, 403)