.obf/.obz is the vendor-neutral OpenAAC/CoughDrop interchange format
Proloquo, Cboard, and CoughDrop already import/export; a board that can't
round-trip it strands its users. Add aac_core::obf with to_obf/from_obf
(single-board .obf JSON).
Mapping: OBF's grid.order (rows x columns of button ids) is exactly aac's
motor-stability invariant — cell positions are explicit and preserved.
Cells <-> buttons; action <-> vocalization / load_board (navigation) /
special-action vocabulary (:backspace, :clear, :speak); colors carried.
What OBF cannot hold (energy/signature provenance, frequency, created_at,
grammar modifiers) is dropped on export, defaulted on import — an
interchange projection, not aac's source of truth. .obz zip deferred (a
thin wrapper, left to a host that already has a zip dep).
3 tests green (open-board shape, full round-trip of positions/labels/
actions/colors incl. navigation + backspace, missing-grid error), clippy
clean. No new deps (serde_json + uuid already present).
Co-Authored-By: Claude Opus 4.8 <[email protected]>
b3c31e1472