Unified Wormhole Accessibility Model

We present a unified, information-first framework for spacetime traversability in which causal accessibility is a transient, control-limited dynamical phase rather than a permanent geometric property. The central operational question is not whether a wormhole geometry exists, but whether a null signal can propagate across a throat before caustic formation closes the path. Using a control-theoretic reduction of the Raychaudhuri equation, we define an accessibility functional Φ that measures cumulative focusing surplus along a null congruence. Accessibility exists only when Φ remains subcritical for a finite affine-parameter interval exceeding a kinematic floor.