Variational Backbone and Regime Closures XI (QM): Quantum Probability as a Retained Readout in the Conservative Reading Hilbert/Born compatibility, measurement update, and Bell audit

This paper places the standard quantum probability and measurement package inside the VBRC representation layer. It does not claim that quantum mechanics is the unique microscopic law of the unread side, nor does it identify the unread coordinate with a hidden physical sector. Under the Internal Invisibility Principle, unread content reaches retained physics only through a licensed summary channel. Part XI therefore starts from an already generated R3 retained channel and asks how that channel becomes a quantum observation instance. The first output is protocol probability: once a normalized retained protocol weight and a readout channel are declared, outcome probabilities are obtained as pushforwards and conditional laws of the observation protocol. The paper then records the additional gates under which this protocol probability is represented by the standard Hilbert/Born package. On the Hilbert-effect branch, the Born trace rule is read as the unique strongly IIP-admissible probability law, because the usual positivity, normalization, affineness, and POVM-additivity requirements function as no-leak conditions against unread refinements, hidden context, preparation history, and raw hidden variables. The standard Born, PVM/POVM, and measurement-update formulas are therefore compatibility readouts of a retained R3 channel, not claims of a unique hidden ontology. A dynamical R2/R3 measurement loop is recorded as a realization of the same trace form. Bell-violating quantum correlations are admitted through the standard bipartite Hilbert/Born readout, while local factorizing hidden-variable representations are incompatible gates for the quantum branch.