v2.15.0 - Wormhole mechanistic check: message-mode participation and operator growth rate (Experiment 13, honest negative result)

Tests two more candidate explanations for the sign-dependent instance variance from Experiments 10/11, this time grounded directly in the protocol implementation rather than a generic aggregate statistic, reusing Experiment 11's own n=100 instance set and delta values (no re-screening needed).

Feature A -- message-mode participation: the Jordan-Wigner mapping (dense_evolution.fermions.majorana_pauli_terms) shows Majorana modes 1 and 2 map onto qubit index 0, exactly the qubit the message is injected into and read out from. Counts how many of each instance's K=10 SYK quads touch those two modes specifically.

Feature B -- operator growth rate: reuses Experiment 12's own Gamma_P/Heisenberg-evolution machinery (run_size_winding_check) to get mean operator size at t=0.7 and t=1.2 -- real, non-trivial, instance-varying data Experiment 12 already computed but never correlated against the sign.

Result: neither correlates. Message-mode participation r=-0.012 (p=0.90); operator growth rate at t=1.2 r=+0.126 (p=0.21). Both are far from the conventional 0.05 threshold -- a clean null on both counts, ruling out a 4th and 5th candidate explanation (on top of Experiment 11's two and Experiment 12's structurally-trivial phase diagnostic). Flagged explicitly: this is the 4th/5th candidate tested on the same n=100 sample used in Experiment 11, a real multiple-comparisons risk that would matter more had either come back significant.

Full write-up: docs/wormhole_syk_teleportation.md#experiment-13-mechanistic-check----message-mode-participation--operator-growth-rate-run-2026-08-07