[cschanhniem]

Summary

• BatchSelectionProposalEntry: 12 fields, gate_passed must be True
• 9 validation rules: BSP- prefix, CRG- gate reference, gate_passed=True enforced, candidate_ids >=1, strategy in 5 valid values, fraction bounds, fraction sum=1.0, Brier bounds, notes length
• 3 warnings: pure exploitation, single candidate, marginal Brier threshold
• 68 tests; BASELINE 4821->4889
• CLI: openamp-foundry batch-selection-proposal-check
• Closes the Phase O calibration loop back to candidate selection