Speculative conceptual note proposing that the relativistic light cone is not a passive geometric boundary but an active dimensional filter that separates unmanifested potential (Bit 0) from observable three-dimensional reality (Bit 1). Within the UAT/UCP framework, the speed of light is reinterpreted as the processing rate of this filter, and the quantum measurement problem is resolved mechanically without invoking observer consciousness. The causal overflow (3.3%), the thermal calibration margin (7%), and the geometric invariant R_geom = 0.2792 are reinterpreted as the thermodynamic costs of the Bit 0 -> Bit 1 transition. The note also formalizes the idea that the light cone marks the boundary of our dimension: processes exceeding the Ivancho limit (kappa_crit = 4.978) remain outside the cone, in the unmanifested domain. This is a theoretical exploration, not a validation. It is internally consistent with the published UAT/UCP constants but remains speculative and has no experimental confirmation.