docs: fix semantic accuracy of README configuration tunables

docs: fix semantic accuracy of README configuration tunables

- polyorder: correct range from int >= 1 to int >= 0 (savgol accepts degree-0)
- robust standardization: replace 'IQR' with '(Q₃-Q₁)' (quantiles are configurable)
- label_weights: broaden scope from 'distance calculations to ideal point' to 'trial selection methods'
- label_p_order: replace 'p-order parameter for distance metrics' with 'Lp exponent for parameterized metrics'
- label_density_aggregation_param: replace 'p-order' with 'Lp exponent' for consistency