Dict-set! keys iterate in scrambled order, so Values|FormEncoded and
Values|JSONString produced output in the wrong order. Fix: hs-values-absorb
now tracks insertion order in a hidden `_order` list on the dict itself.
hs-coerce FormEncoded/JSONString paths read `_order` when present and
iterate in that order (filtering the marker key out).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>