feat: Add Discord forum post support

Add support for creating posts in Discord forum channels (type 15).

Forum channels require a message object when creating threads, unlike
regular threads that are created from existing messages.

Changes:
- Added 'message' parameter to DiscordThreadCreate type
- Updated createThreadDiscord to handle forum posts with message body
- Modified thread-create action to accept and pass message parameter
- Forum posts use direct endpoint: /channels/{channelId}/threads

Usage:
message({
  action: "thread-create",
  channelId: "<forum_channel_id>",
  threadName: "Post Title",
  message: "Post content"
})

Fixes: Forum posts previously failed with 'This field is required' error

src/agents/tools/discord-actions-messaging.ts

@@ -279,6 +279,7 @@ export async function handleDiscordMessagingAction(
       const channelId = resolveChannelId();
       const name = readStringParam(params, "name", { required: true });
       const messageId = readStringParam(params, "messageId");
+      const message = readStringParam(params, "message");
       const autoArchiveMinutesRaw = params.autoArchiveMinutes;
       const autoArchiveMinutes =
         typeof autoArchiveMinutesRaw === "number" && Number.isFinite(autoArchiveMinutesRaw)
@@ -287,10 +288,10 @@ export async function handleDiscordMessagingAction(
       const thread = accountId
         ? await createThreadDiscord(
             channelId,
-            { name, messageId, autoArchiveMinutes },
+            { name, messageId, message, autoArchiveMinutes },
             { accountId },
           )
-        : await createThreadDiscord(channelId, { name, messageId, autoArchiveMinutes });
+        : await createThreadDiscord(channelId, { name, messageId, message, autoArchiveMinutes });
       return jsonResult({ ok: true, thread });
     }
     case "threadList": {

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

@@ -180,6 +180,7 @@ export async function handleDiscordMessageAction(
   if (action === "thread-create") {
     const name = readStringParam(params, "threadName", { required: true });
     const messageId = readStringParam(params, "messageId");
+    const message = readStringParam(params, "message");
     const autoArchiveMinutes = readNumberParam(params, "autoArchiveMin", {
       integer: true,
     });
@@ -190,6 +191,7 @@ export async function handleDiscordMessageAction(
         channelId: resolveChannelId(),
         name,
         messageId,
+        message,
         autoArchiveMinutes,
       },
       cfg,

src/discord/send.messages.ts

@@ -97,6 +97,14 @@ export async function createThreadDiscord(
   if (payload.autoArchiveMinutes) {
     body.auto_archive_duration = payload.autoArchiveMinutes;
   }
+  // Forum channels (type 15) require a message object for thread creation
+  if (payload.message) {
+    body.message = { content: payload.message };
+    // For forum posts, POST directly to /channels/{channelId}/threads
+    const route = `/channels/${channelId}/threads`;
+    return await rest.post(route, { body });
+  }
+  // Regular thread from an existing message
   const route = Routes.threads(channelId, payload.messageId);
   return await rest.post(route, { body });
 }

src/discord/send.types.ts

@@ -68,6 +68,7 @@ export type DiscordMessageEdit = {
 
 export type DiscordThreadCreate = {
   messageId?: string;
+  message?: string;
   name: string;
   autoArchiveMinutes?: number;
 };