Multi-Brand Plans

multi-brand/ holds implementation plans for multi-brand isolation work in servers_v2.

Current plans:

• 2026-04-27-multi-brand-isolation-plan.md — original 16-phase isolation rollout (Phase 1–15 delivered; Phase 16 hard-flip closed by switching compose defaults to enforce).
• 2026-05-05-event-brand-scoping.md — schema-level enforcement of brand_id on every domain event envelope; producer-site cleanup; consumers fail-closed regardless of enforcement mode.
• 2026-05-05-phase-4e-dual-read-sunset.md — removal of the legacy user-session-{account} Redis key and the gateway/player_service dual-read fallback.