v0.6.4

[0.6.4] - 2026-07-10

Changed

• The actuarialpy dependency is now an open floor (>=0.41) instead of a
  capped range (>=0.41.0,<0.45.0). The cap made every actuarialpy minor
  release a resolver conflict until a coordinated re-release here; the
  ecosystem policy is now open floors, with the nightly ecosystem smoke
  workflow catching runtime drift. CI keeps a pinned lane at the 0.41.0
  floor edge.