Bumps FEATURE_DIM 32→40. Slots [32..40] now carry 8 TGN-style Fourier
features encoding the elapsed time Δt = ts_ns - prev_ts_ns:
(cos(ω_k · Δt_ns), sin(ω_k · Δt_ns))_{k=0..3}
at log-spaced periods [60s, 6s, 600ms, 60ms].
This gives Mamba2's input vector explicit Δt encoding that's
discriminative across temporal scales — particularly important once
decision-stride > 1 (Phase 2A) lands and the gap between K-positions
becomes irregular. Without these features the model has no way to
distinguish "1ms gap" from "1s gap" between consecutive K-positions.
Slots [0..32] unchanged (bit-equivalent for the first 32 features).
Reserved-zero slots [26..32] kept for future macro context. Slots
[20..26] still hold the loader-precomputed EMA regime cascade.
Frequencies stored in __constant__ memory (SNAP_DT_OMEGAS[4]) — small
table, broadcast read pattern, no register pressure. Frequency
selection rationale (one per log-decade):
60s — minute-scale macro session context
6s — 10s-scale liquidity windows
600ms — sub-second microstructure
60ms — tick-cluster spacing
Δt clamped to >= 0 so the rare out-of-order timestamp doesn't produce
nonsense angles. Each (cos, sin) pair satisfies cos²+sin² = 1
(verified by new test `dt_fourier_features_are_bounded`).
New tests in snap_feature_bit_equiv.rs:
- dt_fourier_features_are_bounded: |slot| <= 1 + cos²+sin² == 1
- dt_fourier_discriminates_scales: Δt=1ms vs Δt=1s produce L2-distinct
Fourier vectors (>0.1)
- reserved_slots_are_zero updated to check [20..32] (regime + reserved)
instead of [20..FEATURE_DIM]
All 8 perception_overfit smokes still pass (synthetic stride=1 and
stride=4 both converge 0.32 → 0.0000) — proves the wider FEATURE_DIM=40
input doesn't break the Mamba2+LN+GRN chain.
build.rs cache-bust → v8.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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