Energy Filament Theory (EFT) A19: Threshold Events and Decay Chains Protocol Family — Beta Clustering, Threshold Discreteness, Chain Rewriting, and Distance/Off‑Axis Scaling

This record publishes EFT-A19, the “Threshold Events and Decay Chains Protocol Family” in the EFT methods-layer protocol library. A19 standardizes an auditable workflow for P/Pth-driven threshold-discrete event chains, including beta-minus/beta-plus clustering and mirror-sign arbitration (Δtcommon vs pmiss∥), two-station propagation scaling (ΔT≈D/vc), off-axis attenuation and on-axis 1/d decay of the nondispersive common-term step, and (if claimed) rule-level change-point fingerprints in decay rate λ and branching ratios bᵢ (chain rewriting). A19 hard-locks three guardrails aligned to A4 patches (Sx/Ix/Tx) and maps to the audit clause Z13/T11.