Adds two sections to the spec:
- Implementation defaults: pins the four open decisions settled before
Phase 1 (naive baseline = zero-change, math = inline pure PHP,
coefficients on the backtests row, BEIS retrain = manual CSV + cron)
plus the namespace, scaler, and Pest conventions.
- Changelog v3: records the verdict-via-rule-gates architecture (gates
not multipliers), removal of weeks_since_duty_change as a feature,
lower 62% backtest gate, structural leak detector promoted to primary.
Captured here so a future session can resume implementation without
re-deriving them.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
d13a29df01