Aliased (extern alias 'engine') to confine the decompiled engine's large
global-namespace type surface, which would otherwise collide with node types
(BattlePlayer, MessagePackSerializer). Also expose internals to
SVSim.BattleEngine.Tests for the upcoming N0/N1 tests.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>