v0.20.0

Changed

• flash-ansr 0.18: the two-part code is the ranking. Pin flash-ansr>=0.18,<0.19. Every shipped
  scaling config ranks with ranking: {mode: mdl} -- flash-ansr's two-part code
  (n/2) log2 FVU + bits (the score study's S1, owner ruling 2026-09-16) -- instead of the fixed
  mdl_strength: 1.0e-2 (S0) they carried before; a config that still names mdl_strength runs
  the fixed weight, so the old numbers stay reproducible on request. Result files record the
  ranking as before (mdl_strength: null = the two-part code).