Fix WorkspaceFilesClient.Stat() silently swallowing non-404 API errors (#4994)

## Changes
Fix `WorkspaceFilesClient.Stat()` to propagate non-404 API errors
instead of returning zero-value file info with nil error.

## Why
When `Stat()` received a non-404 error (e.g. 403 Forbidden, 500 Internal
Server Error), it fell through the error handling and returned
`(zero-value, nil)`. This caused callers like `workspace export-dir` to
silently succeed without exporting anything, and template init to
incorrectly report that files already exist.

## Tests
Added unit tests covering 403, 500, and 404 error responses from the
workspace get-status API.

Author: denik

libs/filer/workspace_files_client.go

@@ -368,6 +368,8 @@ func (w *WorkspaceFilesClient) Stat(ctx context.Context, name string) (fs.FileIn
 		if aerr.StatusCode == http.StatusNotFound {
 			return nil, fileDoesNotExistError{absPath}
 		}
+
+		return nil, err
 	}
 
 	return stat, nil

libs/filer/workspace_files_client_test.go

@@ -6,7 +6,9 @@ import (
 	"testing"
 	"time"
 
+	"github.com/databricks/cli/libs/testserver"
 	"github.com/databricks/databricks-sdk-go"
+	"github.com/databricks/databricks-sdk-go/apierr"
 	"github.com/databricks/databricks-sdk-go/config"
 	"github.com/databricks/databricks-sdk-go/service/workspace"
 	"github.com/stretchr/testify/assert"
@@ -131,3 +133,51 @@ func TestWorkspaceFilesClient_wsfsUnmarshal(t *testing.T) {
 	assert.False(t, info.IsDir())
 	assert.NotNil(t, info.Sys())
 }
+
+func statWithError(t *testing.T, statusCode int, errorCode string) error {
+	t.Helper()
+
+	server := testserver.New(t)
+	server.Handle("GET", "/api/2.0/workspace/get-status", func(req testserver.Request) any {
+		return testserver.Response{
+			StatusCode: statusCode,
+			Body: map[string]string{
+				"error_code": errorCode,
+				"message":    "test error",
+			},
+		}
+	})
+	testserver.AddDefaultHandlers(server)
+
+	client, err := databricks.NewWorkspaceClient(&databricks.Config{
+		Host:  server.URL,
+		Token: "testtoken",
+	})
+	require.NoError(t, err)
+
+	f, err := NewWorkspaceFilesClient(client, "/test")
+	require.NoError(t, err)
+
+	_, err = f.Stat(t.Context(), "file")
+	require.Error(t, err)
+	return err
+}
+
+func TestWorkspaceFilesClientStatForbidden(t *testing.T) {
+	err := statWithError(t, 403, "PERMISSION_DENIED")
+	var apiErr *apierr.APIError
+	require.ErrorAs(t, err, &apiErr)
+	assert.Equal(t, 403, apiErr.StatusCode)
+}
+
+func TestWorkspaceFilesClientStatInternalError(t *testing.T) {
+	err := statWithError(t, 500, "INTERNAL_ERROR")
+	var apiErr *apierr.APIError
+	require.ErrorAs(t, err, &apiErr)
+	assert.Equal(t, 500, apiErr.StatusCode)
+}
+
+func TestWorkspaceFilesClientStatNotFound(t *testing.T) {
+	err := statWithError(t, 404, "RESOURCE_DOES_NOT_EXIST")
+	assert.ErrorIs(t, err, fs.ErrNotExist)
+}