aitools: Fix default_catalog handling in init-template commands (#4312)

## Changes
Only set `default_catalog` when explicitly provided via `--catalog`
flag.

## Why
Generated projects that used the `default` template were getting an
empty `catalog:` field instead of using the workspace default.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: lennartkats-db

experimental/aitools/cmd/init_template/empty.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 
 	"github.com/databricks/cli/cmd/root"
-	"github.com/databricks/cli/experimental/aitools/lib/middlewares"
 	"github.com/databricks/cli/libs/template"
 	"github.com/spf13/cobra"
 )
@@ -62,16 +61,14 @@ After initialization:
 			return fmt.Errorf("--language must be 'python', 'sql', or 'other', got '%s'", language)
 		}
 
-		// Default to workspace default catalog if not specified
-		if catalog == "" {
-			catalog = middlewares.GetDefaultCatalog(ctx)
-		}
-
 		configMap := map[string]any{
 			"project_name":     name,
 			"personal_schemas": "yes",
 			"language_choice":  language,
-			"default_catalog":  catalog,
+		}
+
+		if catalog != "" {
+			configMap["default_catalog"] = catalog
 		}
 
 		return MaterializeTemplate(ctx, TemplateConfig{

experimental/aitools/cmd/init_template/job.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 
 	"github.com/databricks/cli/cmd/root"
-	"github.com/databricks/cli/experimental/aitools/lib/middlewares"
 	"github.com/databricks/cli/libs/template"
 	"github.com/spf13/cobra"
 )
@@ -50,19 +49,16 @@ After initialization:
 			return errors.New("--name is required. Example: init-template job --name my_job")
 		}
 
-		// Default to workspace default catalog if not specified
-		if catalog == "" {
-			catalog = middlewares.GetDefaultCatalog(ctx)
-		}
-
 		configMap := map[string]any{
 			"project_name":     name,
 			"include_job":      "yes",
 			"include_pipeline": "no",
 			"include_python":   "yes",
 			"serverless":       "yes",
 			"personal_schemas": "yes",
-			"default_catalog":  catalog,
+		}
+		if catalog != "" {
+			configMap["default_catalog"] = catalog
 		}
 
 		return MaterializeTemplate(ctx, TemplateConfig{

experimental/aitools/cmd/init_template/pipeline.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 
 	"github.com/databricks/cli/cmd/root"
-	"github.com/databricks/cli/experimental/aitools/lib/middlewares"
 	"github.com/databricks/cli/libs/template"
 	"github.com/spf13/cobra"
 )
@@ -59,16 +58,14 @@ After initialization:
 			return fmt.Errorf("--language must be 'python' or 'sql', got '%s'", language)
 		}
 
-		// Default to workspace default catalog if not specified
-		if catalog == "" {
-			catalog = middlewares.GetDefaultCatalog(ctx)
-		}
-
 		configMap := map[string]any{
 			"project_name":     name,
 			"personal_schemas": "yes",
 			"language":         language,
-			"default_catalog":  catalog,
+		}
+
+		if catalog != "" {
+			configMap["default_catalog"] = catalog
 		}
 
 		return MaterializeTemplate(ctx, TemplateConfig{