Variational Backbone and Regime Closures XII: Principal-Operator Invariance and Collapse-Route Exclusion Exterior-gate GR, summary-active interior readouts, and period-charge barriers

VBRC treats collapse-route exclusion as a gated interface diagnostic, not as an unrestrictedsingularity-resolution claim. Part XII is aligned with the Part I constitutional order: a laterPart first declares its instance package, then licenses the unread-to-retained summaryF = ΣXII (II ),and only inside a selected representative branch may this summary be written in a first-orderform such as F = D(XII)III .The collapse diagnostic studied here is a further form-valued period readout of thatlicensed summary. In the Part XII package one declares a period representativeω = ΩXII (F), KΣp =ZΣpω.Only in a de Rham-type subcase may one identify ω = F = D(XII)III = dII . Thus the periodcharge is not a universal primitive datum of the unread sector; it is a branch-level periodreadout of a licensed summary.Part XII also separates two geometric readout gates. Ordinary exterior GR is treatedas a summary-suppressed geometric gate: the summary footprint is absent, absorbed, orrepresented as ordinary effective stress. A black-hole interior readout is allowed to besummary-active: the same licensed summary may leave a geometric footprint in the retainedmetric equation. This is not a claim that GR is modified by appending an external correction;it is a gate statement about which readout of the same summary interface remains licensed.The paper records two conditional diagnostics. First, admissible elimination preservesthe principal symbol and characteristic cone, inherited from Part VII. Second, if the declaredperiod charge is nonzero, the localized period-coercivity gate is active, and a finite R2/R3budget gate remains valid, then the route Vol(Σp) → 0 is not licensed. The conclusion isa branch-internal barrier theorem inside IXII , not a Tier-I structural theorem and not auniversal no-singularity theorem. Charge-null sectors, Hawking evaporation, information-lossquestions, and cosmological initial singularity data outside the declared gates remain outsidethe claim.