OptionalidInstance root id (its persistent identity). Minted when omitted.
OptionalparentParent to attach the instance under. Defaults to no parent (caller adds to a scene).
OptionalpositionWorld/local placement overriding the assembly root's authored transform.
OptionalrotationOptionalscaleOptionaloverridesExtra overrides applied to this instance on top of the assembly (e.g. per-spawn tint/scale).
Placement + identity options for instantiateAssembly.