feat(discord): add configurable privileged Gateway Intents (GuildPresences, GuildMembers) (#2266)

* feat(discord): add configurable privileged Gateway Intents (GuildPresences, GuildMembers)

Add support for optionally enabling Discord privileged Gateway Intents
via config, starting with GuildPresences and GuildMembers.

When `channels.discord.intents.presence` is set to true:
- GatewayIntents.GuildPresences is added to the gateway connection
- A PresenceUpdateListener caches user presence data in memory
- The member-info action includes user status and activities
  (e.g. Spotify listening activity) from the cache

This enables use cases like:
- Seeing what music a user is currently listening to
- Checking user online/offline/idle/dnd status
- Tracking user activities through the bot API

Both intents require Portal opt-in (Discord Developer Portal →
Privileged Gateway Intents) before they can be used.

Changes:
- config: add `channels.discord.intents.{presence,guildMembers}`
- provider: compute intents dynamically from config
- listeners: add DiscordPresenceListener (extends PresenceUpdateListener)
- presence-cache: simple in-memory Map<userId, GatewayPresenceUpdate>
- discord-actions-guild: include cached presence in member-info response
- schema: add labels and descriptions for new config fields

* fix(test): add PresenceUpdateListener to @buape/carbon mock

* Discord: scope presence cache by account

---------

Co-authored-by: kugutsushi <kugutsushi@clawd>
Co-authored-by: Shadow <hi@shadowing.dev>

src/discord/monitor/presence-cache.ts

@@ -0,0 +1,52 @@
+import type { GatewayPresenceUpdate } from "discord-api-types/v10";
+
+/**
+ * In-memory cache of Discord user presence data.
+ * Populated by PRESENCE_UPDATE gateway events when the GuildPresences intent is enabled.
+ */
+const presenceCache = new Map<string, Map<string, GatewayPresenceUpdate>>();
+
+function resolveAccountKey(accountId?: string): string {
+  return accountId ?? "default";
+}
+
+/** Update cached presence for a user. */
+export function setPresence(
+  accountId: string | undefined,
+  userId: string,
+  data: GatewayPresenceUpdate,
+): void {
+  const accountKey = resolveAccountKey(accountId);
+  let accountCache = presenceCache.get(accountKey);
+  if (!accountCache) {
+    accountCache = new Map();
+    presenceCache.set(accountKey, accountCache);
+  }
+  accountCache.set(userId, data);
+}
+
+/** Get cached presence for a user. Returns undefined if not cached. */
+export function getPresence(
+  accountId: string | undefined,
+  userId: string,
+): GatewayPresenceUpdate | undefined {
+  return presenceCache.get(resolveAccountKey(accountId))?.get(userId);
+}
+
+/** Clear cached presence data. */
+export function clearPresences(accountId?: string): void {
+  if (accountId) {
+    presenceCache.delete(resolveAccountKey(accountId));
+    return;
+  }
+  presenceCache.clear();
+}
+
+/** Get the number of cached presence entries. */
+export function presenceCacheSize(): number {
+  let total = 0;
+  for (const accountCache of presenceCache.values()) {
+    total += accountCache.size;
+  }
+  return total;
+}