V.P132 — Truncation-Pipeline Coherence

All pipeline objects commute with truncation maps: for every refinement depth n and every pipeline object F in {G_tau, Phi_TOV, C}, the diagram F|_{n+1} ∘ trunc_{n+1→n} = trunc_{n+1→n} ∘ F|_{n+1} commutes. Consolidates truncation-coherence results from ch15 (tau-Einstein, def:ch15-truncation-coherent-descent), ch17 (TOV, prop:ch17-truncation-invariance), and ch19 (calibration ratio Xi_tau, prop:ch19-xi-stable).