fix(render): warn on stderr when function runtimes can't be cleaned up

cmd/crossplane/render/op/cmd.go

@@ -221,6 +221,7 @@ func (c *Cmd) Run(k *kong.Context, log logging.Logger, sp terminal.SpinnerPrinte
 	defer func() {
 		if err := render.StopFunctionRuntimes(ctx, fnAddrs); err != nil {
 			log.Info("Error stopping function runtimes", "error", err)
+			render.WarnCleanupFailure(k.Stderr, err)
 		}
 	}()
 

cmd/crossplane/render/render.go

@@ -20,6 +20,8 @@ package render
 
 import (
 	"context"
+	"fmt"
+	"io"
 	"strings"
 
 	fnv1 "github.com/crossplane/function-sdk-go/proto/v1"
@@ -196,3 +198,13 @@ func OverrideFunctionAnnotations(fns []pkgv1.Function, annotations []string) err
 	}
 	return nil
 }
+
+// WarnCleanupFailure writes a short warning about err to w. It does nothing if
+// err is nil. Callers use it to surface function runtime cleanup failures that
+// would otherwise only be visible with --verbose.
+func WarnCleanupFailure(w io.Writer, err error) {
+	if err == nil {
+		return
+	}
+	_, _ = fmt.Fprintf(w, "warning: failed to clean up function runtimes; some resources (e.g. containers) may need to be removed manually: %v\n", err)
+}

cmd/crossplane/render/xr/cmd.go

@@ -281,6 +281,7 @@ func (c *Cmd) Run(k *kong.Context, log logging.Logger, sp terminal.SpinnerPrinte
 	defer func() {
 		if err := render.StopFunctionRuntimes(ctx, fnAddrs); err != nil {
 			log.Info("Error stopping function runtimes", "error", err)
+			render.WarnCleanupFailure(k.Stderr, err)
 		}
 	}()