feat: IRC — add first-class channel support

Adds IRC as a first-class channel with core config surfaces (schema/hints/dock), plugin auto-enable detection, routing/policy alignment, and docs/tests.

Co-authored-by: Vignesh <vigneshnatarajan92@gmail.com>

src/config/types.queue.ts

@@ -12,6 +12,7 @@ export type QueueModeByProvider = {
   whatsapp?: QueueMode;
   telegram?: QueueMode;
   discord?: QueueMode;
+  irc?: QueueMode;
   googlechat?: QueueMode;
   slack?: QueueMode;
   signal?: QueueMode;