Iron Triangle Trace for Longevity (ITT-L): A PACR Application Payload Format for Gene-Level Longevity Data

This document defines Iron Triangle Trace for Longevity (ITT-L), a domain-specific Application Payload Format carried within the PACR (Physical and Causal Auditable Record) envelope. Each ITT-L record binds four measurement facets — gene, mechanism, drug/metabolite, and epigenetic — into a single independently-citable asset with causal predecessor chain (Π) integrity provided by the PACR transport layer. ITT-L is NOT a standalone protocol; it is a payload format that leverages PACR for physical proof (Λ, Landauer cost) and causal ordering (Π chain), and AgentCard for service identity.