Initial commit: notification-elements-demo app

Interactive Angular 19 demo for @sda/notification-elements-ui with
6 sections: Bell & Feed, Notification Center, Inbox, Comments &
Threads, Mention Input, and Full-Featured layout. Includes mock
data, dark mode toggle, and real-time event log.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

node_modules/websocket-extensions/lib/pipeline/pledge.js

@@ -0,0 +1,37 @@
+'use strict';
+
+var RingBuffer = require('./ring_buffer');
+
+var Pledge = function() {
+  this._complete  = false;
+  this._callbacks = new RingBuffer(Pledge.QUEUE_SIZE);
+};
+
+Pledge.QUEUE_SIZE = 4;
+
+Pledge.all = function(list) {
+  var pledge  = new Pledge(),
+      pending = list.length,
+      n       = pending;
+
+  if (pending === 0) pledge.done();
+
+  while (n--) list[n].then(function() {
+    pending -= 1;
+    if (pending === 0) pledge.done();
+  });
+  return pledge;
+};
+
+Pledge.prototype.then = function(callback) {
+  if (this._complete) callback();
+  else this._callbacks.push(callback);
+};
+
+Pledge.prototype.done = function() {
+  this._complete = true;
+  var callbacks = this._callbacks, callback;
+  while (callback = callbacks.shift()) callback();
+};
+
+module.exports = Pledge;