PIC — Causal Authority Transition

The core PIC protocol. An executor E_i holding PCA_i wants to delegate restricted authority to the next executor E_{i+1}. It cannot simply forward PCA_i — PCA is bound to E_i and non-transferable. Instead, E_i requests a freshness challenge (PCC) from the Trust Plane (CAT), constructs a Proof of Continuity (PoC) demonstrating both authority over the predecessor PCA and possession of an attested executor identity, and the CAT mints a new PCA_{i+1} that strictly restricts ops (ops_{i+1} ⊆ ops_i) and is bound to E_{i+1}. p_0 is preserved verbatim. This single mechanism repeats at every hop in a PIC transaction, building the causal chain. References pic-spec.md §4.3 (CAT verification), §5.4 (request binding).