[cschanhniem]

Summary

• CandidateSelectionRationale: 12 fields, auditable record of why candidates were selected for a batch
• 12 validation rules: CSR- prefix, pipeline_version+batch_id non-empty, BSP- prefix, ISO date, strategy vocab (4: exploit/explore/diversity/mixed), candidate_count ≥1, count/ids consistency check, ranking_method vocab (6 values), calibration_gate_passed=True enforced, rationale non-empty and ≤400 chars, notes ≤300 chars
• 3 warnings: large batch (>20), random_balanced without notes, expert_review without notes
• 63 tests; BASELINE 5603->5666
• CLI: openamp-foundry candidate-selection-rationale-check
• Implements Phase K K1 — enforces calibration→selection dependency and makes selection decisions auditable