Get the status and results of a walk-forward analysis run. Poll after walk_forward() returns until status="completed" or "failed".

Args — walk_forward_id from walk_forward().

Level 1 (no sweep) returns:

• oos_sharpe_mean / oos_sharpe_std — mean and std of out-of-sample Sharpe across windows
• pct_profitable_windows — fraction of OOS windows with positive return
• per_window — per-window range, sharpe, total_return, trades

Level 2 (with sweep) additionally returns:

• wfe_mean — mean Walk-Forward Efficiency (OOS Sharpe / IS Sharpe); closer to 1.0 means OOS tracked in-sample
• parameter_stability — selected parameter values per param key, one per valid in-sample window
• per_window — is_range, oos_range, is_sharpe, oos_sharpe, wfe, selected_params