fix(discord): normalize bare numeric IDs in outbound target resolution

Bare numeric Discord IDs (e.g. '1470130713209602050') in cron
delivery.to caused 'Ambiguous Discord recipient' errors and silent
delivery failures.

Adds normalizeDiscordOutboundTarget() to the existing Discord
normalize module (channels/plugins/normalize/discord.ts) alongside
normalizeDiscordMessagingTarget. Defaults bare numeric IDs to
'channel:<id>', matching existing behavior.

Both the Discord extension plugin and standalone outbound adapter
use the shared helper via a one-liner resolveTarget.

Fixes #14753. Related: #13927

extensions/discord/src/channel.ts

@@ -16,6 +16,7 @@ import {
   migrateBaseNameToDefaultAccount,
   normalizeAccountId,
   normalizeDiscordMessagingTarget,
+  normalizeDiscordOutboundTarget,
   PAIRING_APPROVED_MESSAGE,
   resolveDiscordAccount,
   resolveDefaultDiscordAccountId,
@@ -291,6 +292,7 @@ export const discordPlugin: ChannelPlugin<ResolvedDiscordAccount> = {
     chunker: null,
     textChunkLimit: 2000,
     pollMaxOptions: 10,
+    resolveTarget: ({ to }) => normalizeDiscordOutboundTarget(to),
     sendText: async ({ to, text, accountId, deps, replyToId, silent }) => {
       const send = deps?.sendDiscord ?? getDiscordRuntime().channel.discord.sendMessageDiscord;
       const result = await send(to, text, {