FIX -- velocity with an EXPECTATIONS channel (what actually causes spirals)

  scenario                                   pi_real  pi_exp  shock  V index
  benign Mode A (anchored expectations)        -1.9%   -1.9%   0.0%    0.991
  expectations un-anchor (deflation deepens)   -1.9%   -5.0%   0.0%    0.975
  confidence shock (precautionary hoarding)    -1.9%   -1.9%   6.0%    0.961
  both: un-anchor + shock (spiral tail)        -1.9%   -5.0%   6.0%    0.946

  Now it behaves: anchored mild deflation -> velocity ~baseline (no action, correct).
  Expectations un-anchoring or a confidence shock -> velocity drops 5-15% -> the
  conditional tail the tool is FOR. This matches the history: Worgl/1930s scrip
  worked in a CONFIDENCE-COLLAPSE deflation, not in benign productivity deflation.

VERIFY -- does demurrage restore velocity in the spiral tail, within leakage?
  scenario                       V no delta   delta V with delta leak-safe?
  expectations un-anchor (deflation deepens)      0.975    4.0%        0.995     AT CAP
  confidence shock (precautionary hoarding)      0.961    4.0%        0.981     AT CAP
  both: un-anchor + shock (spiral tail)      0.946    4.0%        0.966     AT CAP

  Reading: in the un-anchoring case the needed delta (~5%) is ABOVE the conservative
  national leakage ceiling (~4%), so demurrage can only PARTIALLY offset a deep
  expectations spiral before flight dominates -- it is a damper, not a clamp. In the
  confidence-shock case the needed offset is within the ceiling. So demurrage helps
  most against PRECAUTIONARY hoarding shocks and is leakage-limited against a full
  expectations un-anchoring -- which is exactly where you'd ALSO want other tools.
  HONEST: demurrage buys partial velocity insurance in the tail, bounded by leakage;
  it is not a complete answer to a deep deflation-expectations spiral on its own.

VERIFY -- trigger now fires correctly
  benign Mode A (anchored expectations)      V=0.991 -> dormant
  expectations un-anchor (deflation deepens) V=0.975 -> dormant
  confidence shock (precautionary hoarding)  V=0.961 -> dormant
  both: un-anchor + shock (spiral tail)      V=0.946 -> ARM

  Trigger fires in the spiral tail, stays dormant in benign Mode A. Consistent.
