fix(discord): support applied_tags parameter for forum thread creation

Forum channels that require tags fail with "A tag is required" when
creating threads because there was no way to pass tag IDs. Add
appliedTags parameter to the thread-create action so forum posts can
include required tags from the channel's available_tags list.

src/channels/plugins/actions/discord/handle-action.ts

@@ -230,6 +230,7 @@ export async function handleDiscordMessageAction(
     const autoArchiveMinutes = readNumberParam(params, "autoArchiveMin", {
       integer: true,
     });
+    const appliedTags = readStringArrayParam(params, "appliedTags");
     return await handleDiscordAction(
       {
         action: "threadCreate",
@@ -239,6 +240,7 @@ export async function handleDiscordMessageAction(
         messageId,
         content,
         autoArchiveMinutes,
+        appliedTags: appliedTags ?? undefined,
       },
       cfg,
       actionOptions,