docs(pdftract-44isc): verify AcroForm Ch choice value extraction complete
The choice field value extraction module (value_choice.rs) was already
fully implemented with:
- ChoiceKind enum (Combo vs List via /Ff bit 18)
- ChoiceValue enum (Single vs Multiple selections)
- ChoiceValueData struct with kind, selected, default, options, multi_select
- extract_choice_value() handling /V, /DV, /Opt, /Ff parsing
- 33 comprehensive tests
All acceptance criteria met:
✅ Combo with simple /Opt strings
✅ Combo with export/display /Opt pairs
✅ List with multi-select array /V
✅ Empty /Opt handling
✅ Missing /V handling
Integration verified in forms/mod.rs and combiner.rs. No code changes
required - implementation was already complete.
Bead: pdftract-44isc
756fabdb1d