test: ~11 stub-masked assertion failures surfaced by #12441 (redis_service_manager_slm, command_extraction, mcp_isolation_config, workflow_io, queue_integration, notification_suppression) #12443

Surfaced by #12441 (masked by conftest services MagicMock stub) — triage needed

Real-loading services.* submodules (PR #12441, #12438) unmasked these test failures. Each is either real behavior-drift OR a stale test expectation — triage + fix per module (none out of scope). Assertion details:

• redis_service_manager_slm_test.py (4):
  • TestInit::test_defaults_from_env — slm_url resolves to 'http://127.0.0.1:8000', test expects 'https://slm.test' (env-default drift).
  • TestSlmServiceAction::test_raises_when_no_slm_url — no longer raises.
  • TestCheckRedisConnectivity ×2 — patch target services.redis_service_manager.get_redis_client but the module has no such attribute (stale patch target → likely test bug).
• command_extraction_service_test.py::TestSlmExec::test_returns_false_when_no_slm_url — expects "SLM_URL not configured" in stderr; stderr is ''.
• mcp_isolation_config_test.py::TestResolveMode::test_unknown_bridge_uses_global — resolve_mode('http_client_mcp') returns 'inprocess', expected 'subprocess'.
• workflow_io_test.py::TestToCsv::test_empty_step_results — len(lines) == 3, expected 1 (CSV header emitted for empty results).
• queue_integration_test.py::test_queue_integration — AssertionError: Failed to add command to queue.
• test_notification_suppression.py (2): TestNotificationSuppressionConfig::test_should_not_suppress_recent_ci_activity (suppressed True, expected False); TestNotificationSuppressionManager::test_get_summary (summary['suppressed'] == 1, expected 0).

For each: determine real-drift (fix code) vs stale-test (fix test), then fix. Refs #12438. Surfaced by #12441.