Screen protein sequence for potential T-cell epitopes (MHC-II binding). Scans 9-mer windows against 8 common HLA-DRB1 alleles using positional scoring matrices. A window counts as an epitope when it clears an absolute, background-calibrated score threshold (each allele flags at most 5% of random 9-mers of natural composition), so epitope_density is comparable between sequences: a sequence of random natural composition scores ~0.09 against this panel. Deimmunization suggestions target the P1/P4/P6/P9 anchor positions that drive binding. This is an in-silico binding prediction from hand-curated matrices, NOT an ADA rate and not calibrated against measured affinities.

Parameters:
  sequence: Protein amino acid sequence.
  alleles: Optional HLA allele list (default: 8 common DRB1 alleles).

Returns: {n_epitopes, epitopes: [{position, peptide, allele, score, binding_alleles}], epitope_density, risk_classification (low <0.18, moderate <0.27, high), hotspots, per_allele_scores, deimmunization_suggestions: [{position, original_aa, suggested_aa, position_class, predicted_reduction}], binder_thresholds, threshold_basis}