feat: Discord + Instagram integrations

Discord Bot API
- New client: src/clients/discord.ts
- Tools: discord_get_me, discord_get_guilds, discord_get_channels, discord_send_message, discord_get_messages
- REST endpoints: GET /api/discord/me, /api/discord/guilds, /api/discord/channels, /api/discord/messages, POST /api/discord/message
- Multi-account env var: DISCORD_{ACCOUNT}_BOT_TOKEN

Instagram Graph API
- New client: src/clients/instagram.ts
- Tools: instagram_get_profile, instagram_get_media, instagram_create_post
- REST endpoints: GET /api/instagram/profile, /api/instagram/media, POST /api/instagram/post
- Multi-account env vars: INSTAGRAM_{ACCOUNT}_ACCESS_TOKEN, INSTAGRAM_{ACCOUNT}_BUSINESS_ACCOUNT_ID

Total tools: 32

src/clients/discord.ts

@@ -0,0 +1,101 @@
+const DISCORD_API_BASE = 'https://discord.com/api/v10';
+
+function getToken(account: string): string {
+  const envKey = `DISCORD_${account.toUpperCase()}_BOT_TOKEN`;
+  return process.env[envKey] ?? '';
+}
+
+async function discordRequest(
+  token: string,
+  endpoint: string,
+  method: 'GET' | 'POST' = 'GET',
+  body?: unknown
+) {
+  const url = `${DISCORD_API_BASE}${endpoint}`;
+  const res = await fetch(url, {
+    method,
+    headers: {
+      'Authorization': `Bot ${token}`,
+      'Content-Type': 'application/json',
+    },
+    body: body ? JSON.stringify(body) : undefined,
+    signal: AbortSignal.timeout(15000),
+  });
+
+  if (!res.ok) {
+    const error = await res.text();
+    throw new Error(`Discord API error (${res.status}): ${error}`);
+  }
+
+  return res.json();
+}
+
+export async function getMe(args: { account?: string }): Promise<{
+  id: string;
+  username: string;
+  bot: boolean;
+}> {
+  const token = getToken(args.account ?? 'default');
+  if (!token) {
+    throw new Error('Missing Discord credentials. Set DISCORD_{ACCOUNT}_BOT_TOKEN');
+  }
+  return discordRequest(token, '/users/@me');
+}
+
+export async function getGuilds(args: { account?: string }): Promise<Array<{
+  id: string;
+  name: string;
+  icon?: string;
+}>> {
+  const token = getToken(args.account ?? 'default');
+  if (!token) {
+    throw new Error('Missing Discord credentials. Set DISCORD_{ACCOUNT}_BOT_TOKEN');
+  }
+  return discordRequest(token, '/users/@me/guilds');
+}
+
+export async function getChannels(args: { guild_id: string; account?: string }): Promise<Array<{
+  id: string;
+  name: string;
+  type: number;
+}>> {
+  const token = getToken(args.account ?? 'default');
+  if (!token) {
+    throw new Error('Missing Discord credentials. Set DISCORD_{ACCOUNT}_BOT_TOKEN');
+  }
+  return discordRequest(token, `/guilds/${args.guild_id}/channels`);
+}
+
+export async function sendMessage(args: {
+  channel_id: string;
+  content: string;
+  account?: string;
+}): Promise<{ id: string; channel_id: string }> {
+  const token = getToken(args.account ?? 'default');
+  if (!token) {
+    throw new Error('Missing Discord credentials. Set DISCORD_{ACCOUNT}_BOT_TOKEN');
+  }
+
+  return discordRequest(token, `/channels/${args.channel_id}/messages`, 'POST', {
+    content: args.content,
+  });
+}
+
+export async function getMessages(args: {
+  channel_id: string;
+  limit?: number;
+  account?: string;
+}): Promise<Array<{
+  id: string;
+  content: string;
+  author: { username: string; id: string };
+  timestamp: string;
+}>> {
+  const token = getToken(args.account ?? 'default');
+  if (!token) {
+    throw new Error('Missing Discord credentials. Set DISCORD_{ACCOUNT}_BOT_TOKEN');
+  }
+
+  const limit = args.limit ?? 10;
+  return discordRequest(token, `/channels/${args.channel_id}/messages?limit=${limit}`);
+}