Wavefunction Collapse as Geometric Incidence: A Relativistic Framework for Null Quantum Systems

A relativistic framework in which the measurement event is modelled as a geometric incidence between a null quantum system (a photon, represented over projective null twistor space ℙN) and a timelike observer worldline in Minkowski space. The observer's forward temporal orientation is supplied not thermodynamically but as a discrete geometric datum fixed by the temporal orientability of Minkowski space. Global evolution remains unitary; the only irreversibility is a causal monotone of second-law type with no finite non-relativistic limit. The central claim — that the temporal arrow of collapse can be supplied purely geometrically while preserving unitarity — is stated as a falsifiable question with two valid answers, and the deciding experimentum crucis is specified but not yet executed. The claim is therefore left explicitly open.