Doc: code component output section (#14915)

### What problem does this PR solve?

code component output section

### Type of change

- [x] Documentation Update

docs/guides/agent/agent_component_reference/code.mdx

@@ -98,7 +98,49 @@ If you define output variables here, ensure they are also defined in your code i
 
 ### Output
 
-The defined output variable(s) will be auto-populated here.
+The output is split into two parts:
+
+- **Business**: the business output defined in **Return Value**
+- **System**: runtime fields that are populated automatically, such as `content`, `actual_type`, and `attachments`
+
+For example, the following code generates a simple line chart:
+
+```Python
+def main() -> dict:
+    from pathlib import Path
+
+    import matplotlib
+    matplotlib.use("Agg")
+    import matplotlib.pyplot as plt
+
+    artifacts_dir = Path("artifacts")
+    artifacts_dir.mkdir(parents=True, exist_ok=True)
+
+    x = [1, 2, 3, 4, 5]
+    y = [2, 4, 6, 8, 10]
+
+    output_path = artifacts_dir / "simple_plot.png"
+
+    plt.figure(figsize=(6, 4))
+    plt.plot(x, y, marker="o")
+    plt.title("Simple Line Chart")
+    plt.xlabel("X")
+    plt.ylabel("Y")
+    plt.grid(True)
+    plt.tight_layout()
+    plt.savefig(output_path)
+    plt.close()
+
+    return {
+        "result": "plot generated successfully",
+        "file_path": str(output_path),
+    }
+```
+![](https://raw.githubusercontent.com/infiniflow/ragflow-docs/main/images/codeexec_output1.jpg)
+
+Business Output shows the return value you defined, while System Output shows the generated `content`, the inferred `actual_type`, and the collected `attachments`.
+
+![](https://raw.githubusercontent.com/infiniflow/ragflow-docs/main/images/codeexec_output2.jpg)
 
 ## Troubleshooting