devbox: Add setup-ssh-agent-forwarding and offer that in ssh and code

Add a command to setup SSH agent forwarding for devbox ssh endpoints.
Offer to do that in nsc devbox ssh and nsc devbox code.

internal/cli/cmd/devbox/common.go

@@ -7,8 +7,10 @@ package devbox
 import (
 	"context"
 	"fmt"
+	"io"
 
 	devboxv1beta "buf.build/gen/go/namespace/cloud/protocolbuffers/go/proto/namespace/private/devbox"
+	"github.com/kr/text"
 	"namespacelabs.dev/foundation/internal/console"
 	"namespacelabs.dev/foundation/internal/fnapi"
 	"namespacelabs.dev/foundation/internal/providers/nscloud/api/private"
@@ -71,3 +73,7 @@ func doEnsureDevbox(ctx context.Context, devboxClient *private.DevBoxServiceClie
 		regionalSshEndpoint: resp.RegionalSshEndpoint,
 	}, nil
 }
+
+func indent(w io.Writer) io.Writer {
+	return text.NewIndentWriter(w, []byte("    "))
+}

internal/cli/cmd/devbox/describe.go

@@ -12,7 +12,6 @@ import (
 
 	devboxv1beta "buf.build/gen/go/namespace/cloud/protocolbuffers/go/proto/namespace/private/devbox"
 	"github.com/dustin/go-humanize"
-	"github.com/kr/text"
 	"github.com/spf13/cobra"
 	"namespacelabs.dev/foundation/internal/cli/fncobra"
 	"namespacelabs.dev/foundation/internal/console"
@@ -70,7 +69,3 @@ func describeToWriter(out io.Writer, devbox *devboxv1beta.DevBox) {
 	fmt.Fprintln(bodyWriter, "Base image:\t", devbox.GetDevboxSpec().GetBaseImageRef())
 	fmt.Fprintln(bodyWriter, "SSH endpoint:\t", devbox.GetDevboxStatus().GetSshEndpoint())
 }
-
-func indent(w io.Writer) io.Writer {
-	return text.NewIndentWriter(w, []byte("    "))
-}

internal/cli/cmd/devbox/devbox.go

@@ -22,6 +22,7 @@ func NewDevBoxCmd() *cobra.Command {
 	cmd.AddCommand(newEnsureCommand())
 	cmd.AddCommand(newSshCommand())
 	cmd.AddCommand(newVscodeCommand())
+	cmd.AddCommand(newSetupSshAgentForwardingCommand())
 
 	return cmd
 }

internal/cli/cmd/devbox/ssh.go

@@ -38,6 +38,10 @@ func sshDevbox(ctx context.Context, tag string) error {
 		return err
 	}
 
+	if err := offerSetupSshAgentForwarding(ctx); err != nil {
+		return err
+	}
+
 	cmd := exec.Command("ssh", instance.regionalSshEndpoint)
 	cmd.Stdout = os.Stdout
 	cmd.Stdin = os.Stdin