Add --debug flag for WebSocket connection diagnostics

Shows WS URL, auth headers (truncated), full handshake request/response.
Also improves the handshake failure error to include the raw server response.

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

lib/portainer_cli.rb

@@ -39,6 +39,7 @@ module PortainerCli
     HELP
 
     def self.run(argv)
+      debug = argv.delete('--debug')
       config = Config.load
       cmd    = argv.shift&.downcase
 
@@ -56,11 +57,11 @@ module PortainerCli
       when 'console'
         require_config!(config)
         client = Client.new(config)
-        Commands::Console.new(config, client).run(argv)
+        Commands::Console.new(config, client, debug: debug).run(argv)
       when 'exec', 'shell'
         require_config!(config)
         client = Client.new(config)
-        Commands::Exec.new(config, client).run(argv)
+        Commands::Exec.new(config, client, debug: debug).run(argv)
       when 'version', '--version', '-v'
         puts "portainer-cli #{PortainerCli::VERSION}"
       when 'help', '--help', '-h', nil