Fix critical hold issue preventing call disconnections

- Enhanced call leg detection logic for browser phone calls
- Added comprehensive logging for debugging hold/resume operations
- Fixed hold to properly identify customer vs agent call legs
- Added fallback mechanisms when call relationships are unclear
- Improved resume logic to match hold behavior
- Prevents customer disconnections when agent puts call on hold

🤖 Generated with [Claude Code](https://claude.ai/code)

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

includes/class-twp-core.php

@@ -204,6 +204,7 @@ class TWP_Core {
         // Call control actions
         $this->loader->add_action('wp_ajax_twp_toggle_hold', $plugin_admin, 'ajax_toggle_hold');
         $this->loader->add_action('wp_ajax_twp_transfer_call', $plugin_admin, 'ajax_transfer_call');
+        $this->loader->add_action('wp_ajax_twp_get_transfer_agents', $plugin_admin, 'ajax_get_transfer_agents');
         $this->loader->add_action('wp_ajax_twp_requeue_call', $plugin_admin, 'ajax_requeue_call');
         $this->loader->add_action('wp_ajax_twp_start_recording', $plugin_admin, 'ajax_start_recording');
         $this->loader->add_action('wp_ajax_twp_stop_recording', $plugin_admin, 'ajax_stop_recording');