Evaluate a paper trading session against its benchmark and record the result. This is a mutation, not a cheap read — it computes and persists validation metrics.

Returns — a readiness status (whether minimum trades/bars/days criteria are met) plus a metrics dict:

• paper_win_rate, paper_total_return, paper_trades, paper_bars
• benchmark_win_rate, benchmark_total_return, benchmark_max_drawdown, benchmark_sharpe, benchmark_trade_count
• overfitting_context.iteration_count (number of backtests at promotion time)

No verdict is returned. Compare the paper and benchmark numbers yourself and decide whether the strategy is ready for live promotion.