Mailglass-backed email adapter for Chimeway outbound delivery.
Product-facing name: Chimeway.Adapter.Mailglass (see ECOS-01). Implementation
module: Chimeway.Adapters.Mailglass (D-07).
Mailglass requires Elixir ~> 1.18 when enabled. Chimeway core compiles on 1.17+; run mailglass adapter tests on Elixir 1.18+ (see Phase 54 research).
Webhook callbacks are Phase 55.