nx_adnet_invoice_gate.nx

nx_adnet_invoice_gate.nx -- GATE for the billing pipeline (nx_adnet_invoice). Independent re-derivation over fixture journals, not a call into the code under test to describe itself. The teeth that matter are the REFUSALS -- a biller is dangerous in the direction of over-charging: * an ad with NO rate row must emit an explicit REFUSED line, never a zero-priced or omitted one * an ad measured but never viewable must bill 0, not its served count * a rate card with a malformed number must REFUSE, not parse-to-zero * SPEND (the number a budget ceiling consumes) must be UNMEASURABLE rather than 0 when unpriced -- assuming zero spend is exactly how an exhausted campaign keeps serving expect_exit: 0 license_tier: ORIGINAL