Add instructions kwarg to docs

docs/content/docs/agent-sdk/agent-loops.mdx

@@ -136,6 +136,8 @@ The `ComputerAgent` constructor provides a wide range of options for customizing
   Enables prompt caching for repeated prompts (mainly for Anthropic models).
 - `max_trajectory_budget` (`float` | `dict`):
   If set (float or dict), adds a budget manager callback that tracks usage costs and stops execution if the budget is exceeded. Dict allows advanced options (e.g., `{ "max_budget": 5.0, "raise_error": True }`).
+- `instructions` (`str` | `list[str]`):
+  System instructions for the agent. Can be a single string or multiple strings in a tuple/list for readability; they are concatenated into one system prompt.
 - `**kwargs` (`any`):
   Any additional keyword arguments are passed through to the agent loop or model provider.
 
@@ -156,7 +158,11 @@ agent = ComputerAgent(
     max_retries=5,
     screenshot_delay=1.0,
     use_prompt_caching=True,
-    max_trajectory_budget={"max_budget": 5.0, "raise_error": True}
+    max_trajectory_budget={"max_budget": 5.0, "raise_error": True},
+    instructions=(
+        "You are a helpful computer-using agent"
+        "Output computer calls until you complete the given task"
+    )
 )
 ```