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/@npmcli/run-script/lib/is-server-package.js

@@ -0,0 +1,11 @@
+const { stat } = require('node:fs/promises')
+const { resolve } = require('node:path')
+
+module.exports = async path => {
+  try {
+    const st = await stat(resolve(path, 'server.js'))
+    return st.isFile()
+  } catch (er) {
+    return false
+  }
+}