fix: forward threadId to Slack read action

extensions/slack/src/channel.ts

@@ -337,6 +337,7 @@ export const slackPlugin: ChannelPlugin<ResolvedSlackAccount> = {
             limit,
             before: readStringParam(params, "before"),
             after: readStringParam(params, "after"),
+            threadId: readStringParam(params, "threadId"),
             accountId: accountId ?? undefined,
           },
           cfg,