fix(component,ai,gemini): add operation validation for cache task (#1130)

Because

- The cache task was missing validation for the required `operation`
field, which could lead to runtime errors or unexpected behavior when
users don't specify which cache operation to perform

This commit

- Adds validation to check if the `operation` field is specified before
proceeding with cache operations

Author: pinglin

pkg/component/ai/gemini/v0/task_cache.go

@@ -17,6 +17,13 @@ func (e *execution) cache(ctx context.Context, job *base.Job) error {
 		return nil
 	}
 
+	// Check if operation is specified
+	if in.Operation == "" {
+		err := fmt.Errorf("caching operation is not specified")
+		job.Error.Error(ctx, err)
+		return nil
+	}
+
 	// Create Gemini client
 	client, err := e.createGeminiClient(ctx)
 	if err != nil {