feat: add base channel

src/channel/base.ts

@@ -0,0 +1,11 @@
+import type { Brain } from "@/brain";
+import type { AvailabilityStatus } from "@/openrouter/schema";
+
+export interface BaseChannel {
+  readonly brain: Brain;
+
+  init(): Promise<void>;
+
+  send(text: string, opts?: { replyTo?: string }): Promise<void>;
+  setAvailability(status: AvailabilityStatus): Promise<void>;
+}