add channel renderer + try to simplify adapter generics

library/internal/command-reply-renderer.ts

@@ -0,0 +1,22 @@
+import type { CommandInteraction } from "./interaction"
+import type { Message, MessageOptions } from "./message"
+import { Renderer } from "./renderer"
+
+// keep track of interaction ids which have replies,
+// so we know whether to call reply() or followUp()
+const repliedInteractionIds = new Set<string>()
+
+export class CommandReplyRenderer extends Renderer {
+  constructor(private interaction: CommandInteraction) {
+    super()
+  }
+
+  protected createMessage(options: MessageOptions): Promise<Message> {
+    if (repliedInteractionIds.has(this.interaction.id)) {
+      return this.interaction.followUp(options)
+    }
+
+    repliedInteractionIds.add(this.interaction.id)
+    return this.interaction.reply(options)
+  }
+}