ConstReadonlyANY: symbolCatch-all tag for canvases without a specific role.
ReadonlyBACKGROUND: symbolBackground canvas (drawn behind the main one).
ReadonlyDEFAULT: symbolGeneric placeholder tag — distinct from ANY so consumers can differentiate.
ReadonlyMAIN: symbolPrimary render target. Exactly one canvas must be registered with this type before CanvasManager.finishSetup.
Role tags for canvases passed to CanvasManager.setupCanvas. Only
MAINis enforced (exactly one); the others are free-form labels you can use to group background/overlay canvases.