clients: document supervisory/array-write parity gotchas and add advise-supervisory to all CLIs

A consuming project hit two MXAccess parity surprises: a plain Write only
records its user_id when the item has an active supervisory advise (the path
to take when not authenticating), and array writes replace the whole array
rather than patching individual elements. Document both across the five client
READMEs and gateway.md's compatibility baseline, and expose the missing
advise-supervisory subcommand in the go/python/rust/java CLIs (plus the .NET
help text) so callers can establish the supervisory advise without dropping to
the raw command API.

clients/go/cmd/mxgw-go/main.go

@@ -21,6 +21,7 @@ import (
 	"syscall"
 	"time"
 
+	pb "gitea.dohertylan.com/dohertj2/mxaccessgw/clients/go/internal/generated"
 	"gitea.dohertylan.com/dohertj2/mxaccessgw/clients/go/mxgateway"
 	"google.golang.org/protobuf/encoding/protojson"
 	"google.golang.org/protobuf/reflect/protoreflect"
@@ -87,6 +88,8 @@ func runWithIO(ctx context.Context, args []string, stdout, stderr io.Writer) err
 		return runAddItem(ctx, args[1:], stdout, stderr)
 	case "advise":
 		return runAdvise(ctx, args[1:], stdout, stderr)
+	case "advise-supervisory":
+		return runAdviseSupervisory(ctx, args[1:], stdout, stderr)
 	case "subscribe-bulk":
 		return runSubscribeBulk(ctx, args[1:], stdout, stderr)
 	case "unsubscribe-bulk":
@@ -358,6 +361,43 @@ func runAdvise(ctx context.Context, args []string, stdout, stderr io.Writer) err
 	return writeCommandOutput(stdout, *jsonOutput, "advise", options, reply, err)
 }
 
+func runAdviseSupervisory(ctx context.Context, args []string, stdout, stderr io.Writer) error {
+	flags := flag.NewFlagSet("advise-supervisory", flag.ContinueOnError)
+	flags.SetOutput(stderr)
+	common := bindCommonFlags(flags)
+	jsonOutput := flags.Bool("json", false, "write JSON output")
+	sessionID := flags.String("session-id", "", "gateway session id")
+	serverHandle := flags.Int("server-handle", 0, "MXAccess server handle")
+	itemHandle := flags.Int("item-handle", 0, "MXAccess item handle")
+
+	if err := flags.Parse(args); err != nil {
+		return err
+	}
+	if *sessionID == "" {
+		return errors.New("session-id is required")
+	}
+
+	client, options, err := dialForCommand(ctx, common)
+	if err != nil {
+		return err
+	}
+	defer client.Close()
+
+	reply, err := client.Invoke(ctx, &pb.MxCommandRequest{
+		SessionId: *sessionID,
+		Command: &pb.MxCommand{
+			Kind: pb.MxCommandKind_MX_COMMAND_KIND_ADVISE_SUPERVISORY,
+			Payload: &pb.MxCommand_AdviseSupervisory{
+				AdviseSupervisory: &pb.AdviseSupervisoryCommand{
+					ServerHandle: int32(*serverHandle),
+					ItemHandle:   int32(*itemHandle),
+				},
+			},
+		},
+	})
+	return writeCommandOutput(stdout, *jsonOutput, "advise-supervisory", options, reply, err)
+}
+
 func runSubscribeBulk(ctx context.Context, args []string, stdout, stderr io.Writer) error {
 	flags := flag.NewFlagSet("subscribe-bulk", flag.ContinueOnError)
 	flags.SetOutput(stderr)