Step 2 of multi-instancing migration. Both flags now resolve through
BattleAmbient.Current when a scope is active, otherwise hit a static fallback
that preserves today's behavior unchanged for unwrapped callers.
Suite green: SVSim.BattleEngine.Tests pass; SVSim.UnitTests baseline holds.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>