feat(discord): add set-presence action for bot activity and status

Bridge the agent tools layer to the Discord gateway WebSocket via a new
gateway registry, allowing agents to set the bot's activity and online
status. Supports playing, streaming, listening, watching, custom, and
competing activity types. Custom type uses activityState as the sidebar
text; other types show activityName in the sidebar and activityState in
the flyout. Opt-in via channels.discord.actions.presence (default false).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

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

@@ -0,0 +1,105 @@
+import type { Activity, UpdatePresenceData } from "@buape/carbon/gateway";
+import type { AgentToolResult } from "@mariozechner/pi-agent-core";
+import type { DiscordActionConfig } from "../../config/config.js";
+import { getGateway } from "../../discord/monitor/gateway-registry.js";
+import { type ActionGate, jsonResult, readStringParam } from "./common.js";
+
+const ACTIVITY_TYPE_MAP: Record<string, number> = {
+  playing: 0,
+  streaming: 1,
+  listening: 2,
+  watching: 3,
+  custom: 4,
+  competing: 5,
+};
+
+const VALID_STATUSES = new Set(["online", "dnd", "idle", "invisible"]);
+
+export async function handleDiscordPresenceAction(
+  action: string,
+  params: Record<string, unknown>,
+  isActionEnabled: ActionGate<DiscordActionConfig>,
+): Promise<AgentToolResult<unknown>> {
+  if (action !== "setPresence") {
+    throw new Error(`Unknown presence action: ${action}`);
+  }
+
+  if (!isActionEnabled("presence", false)) {
+    throw new Error("Discord presence changes are disabled.");
+  }
+
+  const accountId = readStringParam(params, "accountId");
+  const gateway = getGateway(accountId);
+  if (!gateway) {
+    throw new Error(
+      `Discord gateway not available${accountId ? ` for account "${accountId}"` : ""}. The bot may not be connected.`,
+    );
+  }
+  if (!gateway.isConnected) {
+    throw new Error(
+      `Discord gateway is not connected${accountId ? ` for account "${accountId}"` : ""}.`,
+    );
+  }
+
+  const statusRaw = readStringParam(params, "status") ?? "online";
+  if (!VALID_STATUSES.has(statusRaw)) {
+    throw new Error(
+      `Invalid status "${statusRaw}". Must be one of: ${[...VALID_STATUSES].join(", ")}`,
+    );
+  }
+  const status = statusRaw as UpdatePresenceData["status"];
+
+  const activityTypeRaw = readStringParam(params, "activityType");
+  const activityName = readStringParam(params, "activityName");
+
+  const activities: Activity[] = [];
+
+  if (activityTypeRaw || activityName) {
+    const typeNum = activityTypeRaw ? ACTIVITY_TYPE_MAP[activityTypeRaw.toLowerCase()] : 0;
+    if (typeNum === undefined) {
+      throw new Error(
+        `Invalid activityType "${activityTypeRaw}". Must be one of: ${Object.keys(ACTIVITY_TYPE_MAP).join(", ")}`,
+      );
+    }
+
+    const activity: Activity = {
+      name: activityName ?? "",
+      type: typeNum,
+    };
+
+    // Streaming URL (Twitch/YouTube). May not render for bots but is the correct payload shape.
+    if (typeNum === 1) {
+      const url = readStringParam(params, "activityUrl");
+      if (url) {
+        activity.url = url;
+      }
+    }
+
+    const state = readStringParam(params, "activityState");
+    if (state) {
+      activity.state = state;
+    }
+
+    activities.push(activity);
+  }
+
+  const presenceData: UpdatePresenceData = {
+    since: null,
+    activities,
+    status,
+    afk: false,
+  };
+
+  gateway.updatePresence(presenceData);
+
+  return jsonResult({
+    ok: true,
+    status,
+    activities: activities.map((a) => ({
+      type: a.type,
+      name: a.name,
+      ...(a.url ? { url: a.url } : {}),
+      ...(a.state ? { state: a.state } : {}),
+    })),
+  });
+}