Commands Rules

commands/ is the only place state changes are implemented.
Commands may change persistent ImageDocument state and transient EditorState.
Commands must be deterministic, testable, and side-effect free.
Do not import React, DOM UI, renderer/WebGL internals, storage, network, timers, or filesystem APIs.
Validate payloads before applying changes.
Preserve all core/ and editor/ invariants.
Return the next AppState; do not mutate existing state objects in place.
Every command needs a stable id, clear payload type, and focused responsibility.