[cschanhniem]

Summary

• PredictionDriftEntry: 15 fields tracking mean/std score shifts between reference and evaluation batches
• 8 validation rules: monitor_id prefix DRM-, batch uniqueness, score bounds [0,1], std non-negative, shift magnitude consistency ±0.001, population ≥1, notes length ≤400, notes required when drift_flag=True
• 4 warning conditions: unreported drift (shift ≥0.1 without flag), small populations (<10), variance explosion (eval_std > 2× ref_std)
• fix: enforce uppercase sequence in CandidateSummaryCard validation (pre-existing test failure)
• Phase O O2 complete

Test plan

• make agent-check passes
• All tests pass (1 pre-existing failure fixed: test_lowercase_sequence_fails)