Adds optional projectType discriminator on TProjectMetadata so downstream features (preset pickers, export defaults, UI affordances) can branch on intent without inferring from canvas dimensions.
- New const PROJECT_TYPES and type TProjectType
- TProjectMetadata.projectType (optional for back-compat with stored projects)
- ProjectManager.createNewProject accepts optional projectType, defaults to 'standard'
- Unit tests for PROJECT_TYPES invariants