refactor: centralize message target resolution

Co-authored-by: Thinh Dinh <tobalsan@users.noreply.github.com>

src/channels/plugins/slack.ts

@@ -21,7 +21,7 @@ import {
 } from "./config-helpers.js";
 import { resolveSlackGroupRequireMention } from "./group-mentions.js";
 import { formatPairingApproveHint } from "./helpers.js";
-import { normalizeSlackMessagingTarget } from "./normalize-target.js";
+import { looksLikeSlackTargetId, normalizeSlackMessagingTarget } from "./normalize-target.js";
 import { slackOnboardingAdapter } from "./onboarding/slack.js";
 import { PAIRING_APPROVED_MESSAGE } from "./pairing-message.js";
 import {
@@ -29,7 +29,6 @@ import {
   migrateBaseNameToDefaultAccount,
 } from "./setup-helpers.js";
 import type { ChannelMessageActionName, ChannelPlugin } from "./types.js";
-import { missingTargetError } from "../../infra/outbound/target-errors.js";
 
 const meta = getChatChannelMeta("slack");
 
@@ -205,6 +204,8 @@ export const slackPlugin: ChannelPlugin<ResolvedSlackAccount> = {
   },
   messaging: {
     normalizeTarget: normalizeSlackMessagingTarget,
+    looksLikeTargetId: looksLikeSlackTargetId,
+    targetHint: "<channelId|user:ID|channel:ID>",
   },
   directory: {
     self: async () => null,
@@ -526,16 +527,6 @@ export const slackPlugin: ChannelPlugin<ResolvedSlackAccount> = {
     deliveryMode: "direct",
     chunker: null,
     textChunkLimit: 4000,
-    resolveTarget: ({ to }) => {
-      const trimmed = to?.trim();
-      if (!trimmed) {
-        return {
-          ok: false,
-          error: missingTargetError("Slack", "<channelId|user:ID|channel:ID>"),
-        };
-      }
-      return { ok: true, to: trimmed };
-    },
     sendText: async ({ to, text, accountId, deps, replyToId, cfg }) => {
       const send = deps?.sendSlack ?? sendMessageSlack;
       const account = resolveSlackAccount({ cfg, accountId });