fix(auth): refuse to touch real auth.json during pytest; delete sandbox-escaping test (#14729)

A test in tests/agent/test_credential_pool.py
(test_try_refresh_current_updates_only_current_entry) monkeypatched
refresh_codex_oauth_pure() to return the literal fixture strings
'access-new'/'refresh-new', then executed the real production code path
in agent/credential_pool.py::try_refresh_current which calls
_sync_device_code_entry_to_auth_store → _save_provider_state → writes
to `providers.openai-codex.tokens`. That writer resolves the target via
get_hermes_home()/auth.json. If the test ran with HERMES_HOME unset (direct
pytest invocation, IDE runner bypassing conftest discovery, or any other
sandbox escape), it would overwrite the real user's auth store with the
fixture strings.

Observed in the wild: Teknium's ~/.hermes/auth.json providers.openai-codex.tokens
held 'access-new'/'refresh-new' for five days. His CLI kept working because
the credential_pool entries still held real JWTs, but `hermes model`'s live
discovery path (which reads via resolve_codex_runtime_credentials →
_read_codex_tokens → providers.tokens) was silently 401-ing.

Fixes:
- Delete test_try_refresh_current_updates_only_current_entry. It was the
  only test that exercised a writer hitting providers.openai-codex.tokens
  with literal stub tokens. The entry-level rotation behavior it asserted
  is still covered by test_mark_exhausted_and_rotate_persists_status above.
- Add a seat belt in hermes_cli.auth._auth_file_path(): if PYTEST_CURRENT_TEST
  is set AND the resolved path equals the real ~/.hermes/auth.json, raise
  with a clear message. In production (no PYTEST_CURRENT_TEST), a single
  dict lookup. Any future test that forgets to monkeypatch HERMES_HOME
  fails loudly instead of corrupting the user's credentials.

Validation:
- production (no PYTEST_CURRENT_TEST): returns real path, unchanged behavior
- pytest + HERMES_HOME unset (points at real home): raises with message
- pytest + HERMES_HOME=/tmp/...: returns tmp path, tests pass normally

tests/agent/test_credential_pool.py

@@ -333,66 +333,6 @@ def test_mark_exhausted_and_rotate_persists_status(tmp_path, monkeypatch):
     assert persisted["last_error_code"] == 402
 
 
-def test_try_refresh_current_updates_only_current_entry(tmp_path, monkeypatch):
-    monkeypatch.setenv("HERMES_HOME", str(tmp_path / "hermes"))
-    _write_auth_store(
-        tmp_path,
-        {
-            "version": 1,
-            "credential_pool": {
-                "openai-codex": [
-                    {
-                        "id": "cred-1",
-                        "label": "primary",
-                        "auth_type": "oauth",
-                        "priority": 0,
-                        "source": "device_code",
-                        "access_token": "access-old",
-                        "refresh_token": "refresh-old",
-                        "base_url": "https://chatgpt.com/backend-api/codex",
-                    },
-                    {
-                        "id": "cred-2",
-                        "label": "secondary",
-                        "auth_type": "oauth",
-                        "priority": 1,
-                        "source": "device_code",
-                        "access_token": "access-other",
-                        "refresh_token": "refresh-other",
-                        "base_url": "https://chatgpt.com/backend-api/codex",
-                    },
-                ]
-            },
-        },
-    )
-
-    from agent.credential_pool import load_pool
-
-    monkeypatch.setattr(
-        "hermes_cli.auth.refresh_codex_oauth_pure",
-        lambda access_token, refresh_token, timeout_seconds=20.0: {
-            "access_token": "access-new",
-            "refresh_token": "refresh-new",
-        },
-    )
-
-    pool = load_pool("openai-codex")
-    current = pool.select()
-    assert current.id == "cred-1"
-
-    refreshed = pool.try_refresh_current()
-
-    assert refreshed is not None
-    assert refreshed.access_token == "access-new"
-
-    auth_payload = json.loads((tmp_path / "hermes" / "auth.json").read_text())
-    primary, secondary = auth_payload["credential_pool"]["openai-codex"]
-    assert primary["access_token"] == "access-new"
-    assert primary["refresh_token"] == "refresh-new"
-    assert secondary["access_token"] == "access-other"
-    assert secondary["refresh_token"] == "refresh-other"
-
-
 def test_load_pool_seeds_env_api_key(tmp_path, monkeypatch):
     monkeypatch.setenv("HERMES_HOME", str(tmp_path / "hermes"))
     monkeypatch.setenv("OPENROUTER_API_KEY", "sk-or-seeded")