Expand description
Drift / slew envelope semantics.
The DSFB-native interpretation of drift is the EMA-smoothed residual
magnitude s_k = ρ s_k + (1−ρ)|r_k|; slew is the instantaneous
residual magnitude |r_k|. An envelope is a deterministic threshold band
over both: when s_k > drift_threshold we are in the drift phase; when
additionally |r_k| > slew_threshold we are at a boundary breach.
These are the same definitions used in the dsfb-semiconductor and
dsfb-oil-gas companion crates; we restate them here for clarity rather
than re-import to avoid a cross-crate coupling that would make
dsfb-database harder to publish independently.