refactor(node): de-Qt oaknode and wrap it in a pure C ABI
- copy engine/node (188 files) to src/node/src, de-Qt in waves:
core infra (Node/Param/Value/Variant/mathtypes), project/serializer,
block/output, color, effect leaves, generator, gizmo/plugins
- strip QObject/signals/slots: notifications move to the facade's
oakengine_event channel, ownership becomes explicit (unique_ptr,
add_keyframe/add_gizmo), sender() replaced by current_gizmo
- QVariant replaced by olive::Variant, Qt math types by POD mathtypes,
QXmlStreamReader/Writer by oakcommon's expat-based classes
- sink VideoParams/SubtitleParams/LoopMode/ColorTransform to oakcommon
(M3.5); polygon/text rasterization behind backend hooks
- pure C ABI in include/node + src/node/c_api (oaknode_ prefix,
OAKNODE_E_* codes, undoable variants take OakUndoCommand out-params)
- fix Project::clear() root_ reset + disconnect assert, Sequence
TrackList leak
- 96 gtest cases green in standalone build (build-oaknode)
- docs: signal/slot handling strategy + M3 implementation status
Mike-Solar
d77348ad9f