v1.98.0

Added

• aggregate, agg_fn, and repeats parameters for optimize(), matching the plot_sweep() API. Aggregated dimensions are looped inside the Optuna objective so the optimizer sees robust metrics (e.g. mean loss across seeds or repeated boolean outcomes).
• AGG_FN_MAP in bencher/utils.py — NaN-safe numpy aggregation functions for objective-level aggregation.
• Example example_optimize_aggregate.py demonstrating sweep-then-optimize with dimension aggregation and repeats.

Fixed

• Missing skipna=True on REDUCE and MINMAX repeat aggregation in bench_result_base.py.
• np.mean → np.nanmean in optuna_result.py aggregation to match xarray's NaN-safe behavior.