super-buckets: split tab click (activate) from caret click (dropdown)

Clicking the super-bucket tab now activates the last-shown child
directly. Only the caret arrow on the right opens the dropdown popover.
Caret has its own hit area with accent hover highlight.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

config.php

@@ -1,7 +1,7 @@
 <?php
 
 define('APP_NAME', 'hyprcrd');
-define('APP_VERSION', '1.2.0');
+define('APP_VERSION', '1.3.0');
 
 // Database path — writable directory, outside webroot
 // DB_PATH / UPLOAD_DIR can be pre-defined by the Electron router for app isolation