Fix browser phone client name mismatch causing immediate disconnection

- Standardized client name generation across all files to use alphanumeric only
- Fixed mismatch between token generation and call routing that caused calls to disconnect
- Updated TWP_Workflow, TWP_Webhooks, and TWP_Agent_Manager to use same format
- Client names now consistently formatted as 'agent123Username' without underscores

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

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

includes/class-twp-agent-manager.php

@@ -283,7 +283,12 @@ class TWP_Agent_Manager {
         if ($call_mode === 'browser') {
             // For browser mode, redirect the existing call to the browser client
             $current_user = get_userdata($user_id);
-            $client_name = 'agent_' . $user_id . '_' . sanitize_title($current_user->display_name);
+            // Twilio requires alphanumeric characters only - must match generate_capability_token
+            $clean_name = preg_replace('/[^a-zA-Z0-9]/', '', $current_user->display_name);
+            if (empty($clean_name)) {
+                $clean_name = 'user';
+            }
+            $client_name = 'agent' . $user_id . $clean_name;
             
             // Create TwiML to redirect call to browser client
             $twiml = new \Twilio\TwiML\VoiceResponse();