Theorem: IX-D-ST stage release

Part I proves the causal-interface specification, laboratory-local configuration-support bounds, scalar non-lift, free/causal separation, conditional source-contact incompatibility, conditional subtraction, and normalization audit.

The sharp causal-product release remains Unresolved. No sharp ${\mathsf{TO}}_2$, ${\mathsf{T}}_2$, normalized $R_1$, or $R_2$ is constructed.

Proof. The preceding results establish the stated claims. The future time-ordered hypotheses have not been supplied as a construction, so the subtraction implication cannot be instantiated as an unconditional causal product.