Modernize WordPress Playground testing infrastructure

- Update @wp-playground/cli to v3.0.22 (from deprecated v1.0.28)
- Add bin/playground-test.sh for AI assistant CLI testing
- Add bin/localwp-setup.sh for LocalWP integration
- Create .agents/local-testing-guide.md documentation
- Update blueprints to use new installPlugin step format
- Add npm scripts for playground:start/stop/status
- Add npm scripts for localwp:create/sync/reset
- Update GitHub Actions to use new CLI version
- Use PHP 8.0 and latest WordPress in blueprints

playground/blueprint.json

@@ -1,10 +1,13 @@
 {
   "$schema": "https://playground.wordpress.net/blueprint-schema.json",
-  "landingPage": "/wp-admin/",
+  "landingPage": "/wp-admin/plugins.php",
   "login": true,
+  "preferredVersions": {
+    "php": "8.0",
+    "wp": "latest"
+  },
   "features": {
-    "networking": true,
-    "phpVersion": "7.4"
+    "networking": true
   },
   "steps": [
     {
@@ -12,16 +15,29 @@
       "consts": {
         "WP_DEBUG": true,
         "WP_DEBUG_LOG": true,
-        "WP_DEBUG_DISPLAY": true
+        "WP_DEBUG_DISPLAY": true,
+        "SCRIPT_DEBUG": true
       }
     },
     {
-      "step": "wp-cli",
-      "command": "wp plugin install plugin-toggle --activate"
+      "step": "installPlugin",
+      "pluginData": {
+        "resource": "wordpress.org/plugins",
+        "slug": "plugin-toggle"
+      },
+      "options": {
+        "activate": true
+      }
     },
     {
-      "step": "wp-cli",
-      "command": "wp plugin install kadence-blocks --activate"
+      "step": "installPlugin",
+      "pluginData": {
+        "resource": "wordpress.org/plugins",
+        "slug": "kadence-blocks"
+      },
+      "options": {
+        "activate": true
+      }
     }
   ]
 }