Fix 5 pre-release bugs

- Help text showed wrong config path (~/.portainer-cli vs ~/.config/portainer-cli)
- --port without colon (e.g. --port 8080) crashed with nil/tcp key; now errors clearly
- --cmd used naive split(' ') breaking quoted args; switched to Shellwords.split
- --env without '=' (e.g. --env FOO) silently passed empty value; now errors clearly
- SSL/connection errors surfaced as raw exception; now caught with actionable message

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

lib/portainer_cli/websocket_exec.rb

@@ -40,11 +40,19 @@ module PortainerCli
         ssl             = OpenSSL::SSL::SSLSocket.new(raw, ctx)
         ssl.hostname    = @url.host
         ssl.sync_close  = true
-        ssl.connect
+        begin
+          ssl.connect
+        rescue OpenSSL::SSL::SSLError => e
+          raw.close rescue nil
+          hint = @ssl_verify ? " (try: portainer-cli configure → answer 'n' to SSL verification)" : ""
+          raise "SSL connection failed: #{e.message}#{hint}"
+        end
         ssl
       else
         raw
       end
+    rescue Errno::ECONNREFUSED, Errno::EHOSTUNREACH, SocketError => e
+      raise "Cannot connect to #{@url.host}:#{@url.port} — #{e.message}"
     end
 
     def perform_handshake(socket)