chore: add Playground demo blueprint for PR #922

Seeded demo: 3 failed verification attempts 5 minutes ago,
shows the updated failure notice in context (no rate-limit error).

Landing page: /wp-login.php?action=two_factor_notice_demo

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

Author: dknauss

playground/blueprint.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://playground.wordpress.net/blueprint-schema.json",
+  "preferredVersions": { "php": "8.2", "wp": "latest" },
+  "landingPage": "/wp-login.php?action=two_factor_notice_demo",
+  "steps": [
+    {
+      "step": "installPlugin",
+      "pluginData": {
+        "resource": "url",
+        "url": "https://wordpress-playground-cors-proxy.net/?https://github.com/dknauss/two-factor/archive/refs/heads/ux/notice-mixed-audience.zip"
+      },
+      "options": { "activate": true, "targetFolderName": "two-factor" }
+    },
+    {
+      "step": "writeFile",
+      "path": "/wordpress/wp-content/mu-plugins/two-factor-demo.php",
+      "data": "<?php\nadd_action( 'login_form_two_factor_notice_demo', function () {\n\tif ( ! class_exists( 'Two_Factor_Core' ) || ! class_exists( 'Two_Factor_Email' ) ) {\n\t\twp_die( 'Two-Factor plugin not active.' );\n\t}\n\t$user = get_user_by( 'login', 'tf-demo' );\n\tif ( ! $user ) {\n\t\t$user_id = wp_create_user( 'tf-demo', wp_generate_password(), 'tf-demo@example.com' );\n\t\t$user    = get_user_by( 'id', $user_id );\n\t}\n\tupdate_user_meta( $user->ID, '_two_factor_provider', 'Two_Factor_Email' );\n\tupdate_user_meta( $user->ID, '_two_factor_enabled_providers', array( 'Two_Factor_Email' ) );\n\tupdate_user_meta( $user->ID, Two_Factor_Core::USER_FAILED_LOGIN_ATTEMPTS_KEY, 3 );\n\tupdate_user_meta( $user->ID, Two_Factor_Core::USER_RATE_LIMIT_KEY, time() - 300 );\n\t$login_nonce = Two_Factor_Core::create_login_nonce( $user->ID );\n\tif ( ! $login_nonce ) { wp_die( 'Could not create login nonce.' ); }\n\tTwo_Factor_Core::login_html( $user, $login_nonce['key'], admin_url() );\n\texit;\n} );"
+    }
+  ]
+}