Project domain
Source: src/app/domain/project
ProjectDocument is the versioned top-level save/restore value. It groups
project directories and session documents; each session document records the
video path, frame position, settings, next annotation identifier, and layer
data needed by the project workflow. These are data structures rather than
file operations.
The project store serializes and validates these documents, while the project service reopens videos and restores live sessions. Per-session runtime state is described in Session.