Expand docs/project-file-reference.md to cover the full .ove format
implemented in the current codebase, including:
- Root document and project container structure
- Project data: uuid, plugins, nodes, settings
- Detailed Node serialization (inputs, keyframes, connections, hints,
context, caches)
- Node-specific custom data: Footage proxy/sourcestarttime, ViewerOutput
workarea/markers, Track height, NodeGroup passthroughs
- VideoParams and AudioParams field lists
- MainWindowLayoutInfo layout block
- Partial documents (markers, keyframes, nodes/timeline)
- Versioning and OpenFX notes
All sections are provided in English with Chinese translations.