"_comment": "ECIES thread-key test vector. Generated by test/threadkey.test.mjs from web/static/crypto.js. The Swift LChatTests unwraps wrappedB64 with privPkcs8B64 and must get expectedThreadKeyB64 — a cross-implementation gate so the native ECIES never drifts from the web's. base64url throughout. Regenerate with: node test/threadkey.test.mjs --emit",