Asserts the RFC Q7 prerequisite: every visible form_field has a
form_values row after submit (even null/empty), every absent field has
none. This is the invariant the BindingConflictResolver relies on to
distinguish 'explicit clear' from 'skipped by conditional logic'.
Refs: RFC-WS-6.md §3 (Q7)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>