944a4bef4f
- Fix 1: capture <ValidModifierClass> codes from <ModifiedBy all="false">
and filter each modifier level to only valid codes before cartesian
product; eliminates ~194 phantom codes (e.g. M07.01–03) while keeping
valid ones (M07.00/04/07/09). Split Start/Empty XML event arms to
correctly track children of <ModifiedBy>.
- Fix 2: synthesized para295/para301 inherit parent values; "V" is
promoted to "P" (parent "V" = needs subdivision, terminal is codeable).
Other types ("P", "O", "Z", "") pass through unchanged.
- Fix 3: debug_assert in ModifierClass handler guards against ClaML
document-order assumption changing silently in debug/test builds.
- Fix 4: add expands_single_modifier_chain regression test verifying
C88.00/C88.01 synthesis from a single all="true" ModifiedBy (corpus-
verified: Alpha-ID I30531, I31044).