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/zod-schema.hooks.ts

@@ -23,6 +23,7 @@ export const HookMappingSchema = z
         z.literal("whatsapp"),
         z.literal("telegram"),
         z.literal("discord"),
+        z.literal("irc"),
         z.literal("slack"),
         z.literal("signal"),
         z.literal("imessage"),