Step 4 of multi-instancing migration. Three additional per-battle statics
front-fronted by BattleAmbient.Current, each with a static fallback for
unwrapped callers. ViewerId's SavedataManager-persisting setter is preserved
on the fallback path; inside a scope, the setter is a no-op (the per-battle
perspective is fixed at scope entry).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Step 3 of multi-instancing migration. The dominant per-battle singleton now
resolves through BattleAmbient.Current.Mgr when a scope is active. The legacy
'main' field is renamed _mainFallback and retained for unwrapped callers
(tests, anything not yet scope-wrapped). GetIns() still returns null when
neither is set, preserving the '?.Foo ?? default' patterns in engine code.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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>
Step 1 of the engine multi-instancing migration. Standalone infrastructure;
no engine static reads/writes through it yet. Scope is reentrant (restores
prior on dispose), AsyncLocal flows across awaits, and isolated between
concurrent Task.Run flows.
See docs/superpowers/specs/2026-06-07-engine-multi-instancing-design.md.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
