Feature/default messenger delivery target (openclaw#16985) thanks @KirillShchetinin

Verified:
- pnpm build
- pnpm check
- pnpm test:macmini

Co-authored-by: KirillShchetinin <13061871+KirillShchetinin@users.noreply.github.com>
Co-authored-by: Tak Hoffman <781889+Takhoffman@users.noreply.github.com>

extensions/discord/src/channel.ts

@@ -110,6 +110,8 @@ export const discordPlugin: ChannelPlugin<ResolvedDiscordAccount> = {
         .map((entry) => String(entry).trim())
         .filter(Boolean)
         .map((entry) => entry.toLowerCase()),
+    resolveDefaultTo: ({ cfg, accountId }) =>
+      resolveDiscordAccount({ cfg, accountId }).config.defaultTo?.trim() || undefined,
   },
   security: {
     resolveDmPolicy: ({ cfg, accountId, account }) => {