v0.12.0

Forecast model → v1.2

• The projection interval was over-spread - the complement of the v0.11.1
  fix, not a reversal. That release corrected an under-spread interval by
  widening the rate-uncertainty term. This one corrects a different
  component, the path-noise term: its §5 calibration fit the variance with
  an unweighted regression of squared errors, which is heteroskedastic, so the
  few long-horizon points dominated the fit and inflated it (and the
  over-subtraction silently pinned the rate prior). On real data the over-spread
  was path-dominated, so the two fixes touch orthogonal terms of the same
  interval. v1.2 weights that regression by 1/Δt², calibrating the spread and
  reviving the prior; net, out-of-sample coverage converges toward its 80%
  target. The v1.1 spec is preserved under
  internal/forecast/archive/v1.1/; the
  math is documented in
  internal/forecast/CHANGELOG.md.

• Removed the Low/Medium/High confidence badge. It scored how much recent
  data the forecast had, not how reliable the forecast actually was, so it
  could read "High" next to a wide interval and was uncorrelated with real
  accuracy. The 80% CI already conveys the uncertainty.

New: claumon bench

• An out-of-sample benchmark for the forecast model: leave-one-session-out and
  temporal-holdout protocols, CRPS/pinball proper scoring with coverage, MAE,
  and bias breakdowns, segmented by engagement and horizon. Datasets are
  reproducible: frozen fixtures exported from any device's store
  (claumon bench export --db ...) and seeded synthetic regimes. A development
  and validation tool; it does not affect the dashboard.