Test-only action specs and handler.
_testing_emit_notifications + _testing_notification are kept out of the
production codegen surface (all_action_specs in action_specs.ts).
They register on the live HTTP-RPC + WebSocket dispatchers only when
ZZZ_ENABLE_TEST_ACTIONS=1, which the cross-process test binary
(testing_zzz_server) sets unconditionally and production never does.
In-process unit tests (src/test/server/routes/ws.integration.*.test.ts)
import the specs directly into custom action arrays — no env var needed
since they bypass the production registration path.
Naming follows the test-binary safety convention — _testing_* /
Testing* for anything wire-visible or artifact-shipping, matching
fuz_testing / TestingArgon2idHasher / testing_zzz_server.