Fix macOS containerd timeout on prune --all

- Fast-fail in containerd.New() with os.Stat check before lazy gRPC dial,
  avoiding multi-second timeout when containerd socket is absent (e.g. macOS)
- Make runSystemPruneAll warn-and-skip on per-backend scan/prune failures
  instead of returning an error, so unavailable backends don't abort the
  whole prune operation

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

Author: Karl

internal/cli/system_prune.go

@@ -185,7 +185,8 @@ func runSystemPruneAll(cmd *cobra.Command, dryRun, yes bool) error {
 			return err
 		})
 		if err != nil {
-			return fmt.Errorf("scan %s: %w", b.Name, err)
+			fmt.Fprintf(output, "Warning: scan %s failed: %v\n", b.Name, err) //nolint:errcheck
+			continue
 		}
 		allItems = append(allItems, result.Items...)
 	}
@@ -257,7 +258,7 @@ func runSystemPruneAll(cmd *cobra.Command, dryRun, yes bool) error {
 				return err
 			})
 			if err != nil {
-				return fmt.Errorf("prune %s: %w", name, err)
+				fmt.Fprintf(output, "Warning: prune %s failed: %v\n", name, err) //nolint:errcheck
 			}
 		}
 		if !isJSON {

runtime/containerd/containerd.go

@@ -27,10 +27,17 @@ type Runtime struct {
 var _ runtime.Runtime = (*Runtime)(nil)
 var _ runtime.IsolationValidator = (*Runtime)(nil)
 
+const containerdSock = "/run/containerd/containerd.sock"
+
 // New connects to the containerd daemon and returns a Runtime.
 // It does not validate isolation prerequisites — that is done via ValidateIsolation.
 func New(_ context.Context) (*Runtime, error) {
-	c, err := client.New("/run/containerd/containerd.sock")
+	// Fast-fail if the socket file doesn't exist — avoids a slow dial timeout
+	// on systems where containerd is not installed (e.g. macOS).
+	if _, err := os.Stat(containerdSock); err != nil {
+		return nil, fmt.Errorf("containerd socket not found at %s\n  Is containerd running? Try: sudo systemctl start containerd", containerdSock)
+	}
+	c, err := client.New(containerdSock)
 	if err != nil {
 		return nil, fmt.Errorf("connect to containerd: %w\n  Is containerd running? Try: sudo systemctl start containerd", err)
 	}