fix: filter images by instance type and use image_type slug

- Wizard stepImage now uses GetImagesByInstanceType to show only
  compatible images for the selected instance type (e.g. no CUDA
  images for CPU instances)
- Template edit image picker filters by instance type
- resolveImageName filters by instance type and resolves to
  image_type slug instead of image ID (API expects slug)
- Template edit kind change clears instance type and image when
  they no longer match
- Added back option to instance type picker in template edit

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hi-lei

internal/verda-cli/cmd/template/edit.go

@@ -144,6 +144,13 @@ func buildFieldMenu(tmpl *Template) []editableField {
 					return nil //nolint:nilerr // user canceled
 				}
 				t.Kind = choices[idx]
+				// Clear instance type and image when kind changes — they
+				// may not be compatible with the new kind (e.g. CUDA images
+				// are invalid for CPU instances).
+				if t.InstanceType != "" && !matchKind(t.InstanceType, t.Kind) {
+					t.InstanceType = ""
+				}
+				t.Image = ""
 				return nil
 			},
 		},
@@ -281,9 +288,10 @@ func editInstanceType(ctx context.Context, f cmdutil.Factory, t *Template) error
 		return errors.New("no instance types available")
 	}
 
+	choices = append(choices, "← Back")
 	idx, selErr := f.Prompter().Select(ctx, "Instance type", choices)
-	if selErr != nil {
-		return nil //nolint:nilerr // user canceled
+	if selErr != nil || idx == len(values) {
+		return nil //nolint:nilerr // user canceled or back
 	}
 	t.InstanceType = values[idx]
 	return nil
@@ -323,7 +331,11 @@ func editImage(ctx context.Context, f cmdutil.Factory, t *Template) error {
 	if err != nil {
 		return err
 	}
+	// Filter images by instance type when available.
 	images, err := cmdutil.WithSpinner(ctx, f.Status(), "Loading images...", func() ([]verda.Image, error) {
+		if t.InstanceType != "" {
+			return client.Images.GetImagesByInstanceType(ctx, t.InstanceType)
+		}
 		return client.Images.Get(ctx)
 	})
 	if err != nil {

internal/verda-cli/cmd/vm/template_apply.go

@@ -174,29 +174,44 @@ func resolveTemplateNames(ctx context.Context, ioStreams cmdutil.IOStreams, clie
 	return warnings
 }
 
-// resolveImageName resolves an image name to its ID via the API.
-// For backward compatibility, if the name matches an existing image ID directly,
-// it is used as-is (handles templates created before name-based storage).
+// resolveImageName resolves an image name to its image_type slug via the API.
+// The API expects image_type (e.g. "ubuntu-24.04-cuda-13.0-open-docker"), not
+// the image ID. Filters by instance type when available so incompatible images
+// (e.g. CUDA on CPU) are rejected early with a clear warning.
 func resolveImageName(ctx context.Context, client *verda.Client, name string, opts *createOptions) (warnings []string) {
 	if name == "" {
 		return nil
 	}
-	images, err := client.Images.Get(ctx)
+	var images []verda.Image
+	var err error
+	if opts.InstanceType != "" {
+		images, err = client.Images.GetImagesByInstanceType(ctx, opts.InstanceType)
+	} else {
+		images, err = client.Images.Get(ctx)
+	}
 	if err != nil {
 		return []string{fmt.Sprintf("failed to resolve image name: %v", err)}
 	}
 	// Try matching by name first.
 	for _, img := range images {
 		if img.Name == name {
-			opts.Image = img.ID
+			opts.Image = img.ImageType
+			opts.imageName = img.Name
+			return nil
+		}
+	}
+	// Match by image_type slug (templates may store this directly).
+	for _, img := range images {
+		if img.ImageType == name {
+			opts.Image = img.ImageType
 			opts.imageName = img.Name
 			return nil
 		}
 	}
-	// Backward compat: if the value matches an image ID, use it directly.
+	// Backward compat: if the value matches an image ID, resolve to image_type.
 	for _, img := range images {
 		if img.ID == name {
-			opts.Image = img.ID
+			opts.Image = img.ImageType
 			opts.imageName = img.Name
 			return nil
 		}

internal/verda-cli/cmd/vm/wizard.go

@@ -379,48 +379,54 @@ func stepLocation(getClient clientFunc, cache *apiCache, opts *createOptions, mo
 // --- Step 6: OS Image ---
 
 func stepImage(getClient clientFunc, opts *createOptions) wizard.Step {
-	var imagesByID map[string]string // ID → Name lookup, built by Loader
+	var imageNames map[string]string // ImageType → Name lookup, built by Loader
 	return wizard.Step{
 		Name:        "image",
 		Description: "Operating system image",
 		Prompt:      wizard.SelectPrompt,
 		Required:    true,
-		Loader: func(ctx context.Context, _ tui.Prompter, status tui.Status, _ *wizard.Store) ([]wizard.Choice, error) {
+		DependsOn:   []string{"instance-type"},
+		Loader: func(ctx context.Context, _ tui.Prompter, status tui.Status, store *wizard.Store) ([]wizard.Choice, error) {
 			client, err := getClient()
 			if err != nil {
 				return nil, err
 			}
+			// Filter images by instance type when available.
+			instType, _ := store.Collected()["instance-type"].(string)
 			images, err := cmdutil.WithSpinner(ctx, status, "Loading OS images...", func() ([]verda.Image, error) {
+				if instType != "" {
+					return client.Images.GetImagesByInstanceType(ctx, instType)
+				}
 				return client.Images.Get(ctx)
 			})
 			if err != nil {
 				return nil, fmt.Errorf("fetching images: %w", err)
 			}
-			imagesByID = make(map[string]string, len(images))
+			imageNames = make(map[string]string, len(images))
 			var choices []wizard.Choice
 			for _, img := range images {
 				if img.IsCluster {
 					continue
 				}
-				imagesByID[img.ID] = img.Name
+				imageNames[img.ImageType] = img.Name
 				desc := ""
 				if len(img.Details) > 0 {
 					desc = strings.Join(img.Details, ", ")
 				}
 				choices = append(choices, wizard.Choice{
 					Label:       img.Name,
-					Value:       img.ID,
+					Value:       img.ImageType,
 					Description: desc,
 				})
 			}
 			return choices, nil
 		},
 		Default: func(_ map[string]any) any { return opts.Image },
 		Setter: func(v any) {
-			id := v.(string)
-			opts.Image = id
-			if imagesByID != nil {
-				opts.imageName = imagesByID[id]
+			slug := v.(string)
+			opts.Image = slug
+			if imageNames != nil {
+				opts.imageName = imageNames[slug]
 			}
 		},
 		Resetter: func() { opts.Image = ""; opts.imageName = "" },