feat: Add presence heartbeat for Matrix online status

- matrix-gateway: POST /internal/matrix/presence/online endpoint
- usePresenceHeartbeat hook with activity tracking
- Auto away after 5 min inactivity
- Offline on page close/visibility change
- Integrated in MatrixChatRoom component

node_modules/@pkgjs/parseargs/internal/util.js

@@ -0,0 +1,14 @@
+'use strict';
+
+// This is a placeholder for util.js in node.js land.
+
+const {
+  ObjectCreate,
+  ObjectFreeze,
+} = require('./primordials');
+
+const kEmptyObject = ObjectFreeze(ObjectCreate(null));
+
+module.exports = {
+  kEmptyObject,
+};