Add model to custom agent config docs (#60011)

Co-authored-by: Joe Clark <31087804+jc-clark@users.noreply.github.com>

Author: belaltaher8

content/copilot/reference/custom-agents-configuration.md

@@ -25,6 +25,7 @@ The following table outlines the properties that you can configure for {% data v
 | `description` | **Required** string     | Description of the {% data variables.copilot.copilot_custom_agent_short %}'s purpose and capabilities |
 | `target` | string     | Target environment or context for the {% data variables.copilot.copilot_custom_agent_short %} (`vscode` or `github-copilot`). If unset, defaults to both environments. |
 | `tools`       | list of strings, string | List of tool names the {% data variables.copilot.copilot_custom_agent_short %} can use. Supports both a comma separated string and yaml string array. If unset, defaults to all tools. See [Tools](#tools). |
+| `model`       | string | Model to use when this {% data variables.copilot.copilot_custom_agent_short %} executes. If unset, inherits the default model. |
 | `disable-model-invocation`  | boolean | Disables {% data variables.copilot.copilot_coding_agent %} from automatically using this {% data variables.copilot.copilot_custom_agent_short %} based on task context. When `true`, the agent must be manually selected. Setting `disable-model-invocation: true` is equivalent to `infer: false`. If both are set, `disable-model-invocation` takes precedence. If unset, defaults to `false`. |
 | `user-invocable` | boolean | Controls whether this {% data variables.copilot.copilot_custom_agent_short %} can be selected by a user. When `false`, the agent cannot be manually selected and can only be accessed programmatically. If unset, defaults to `true`. |
 | `infer`       | boolean | **{% data variables.release-phases.retired_caps %}**. Use `disable-model-invocation` and `user-invocable` instead. Enables {% data variables.copilot.copilot_coding_agent %} to automatically use this {% data variables.copilot.copilot_custom_agent_short %} based on task context. When `false`, the agent must be manually selected. If unset, defaults to `true`. |
@@ -37,7 +38,7 @@ Define the agent's behavior, expertise, and instructions in the Markdown content
 
 > [!NOTE]
 >
-> * The `model`, `argument-hint`, and `handoffs` properties from {% data variables.product.prodname_vscode_shortname %} and other IDE {% data variables.copilot.custom_agents_short %} are currently not supported for {% data variables.copilot.copilot_coding_agent %} on {% data variables.product.prodname_dotcom_the_website %}. They are ignored to ensure compatibility.
+> * The `argument-hint` and `handoffs` properties from {% data variables.product.prodname_vscode_shortname %} and other IDE {% data variables.copilot.custom_agents_short %} are currently not supported for {% data variables.copilot.copilot_coding_agent %} on {% data variables.product.prodname_dotcom_the_website %}. They are ignored to ensure compatibility.
 > * For more information on {% data variables.copilot.copilot_custom_agent_short %} file structure in {% data variables.product.prodname_vscode_shortname %}, see [{% data variables.copilot.custom_agents_caps_short %} in {% data variables.product.prodname_vscode_shortname %}](https://code.visualstudio.com/docs/copilot/customization/custom-agents#_custom-agent-file-structure) in the {% data variables.product.prodname_vscode_shortname %} documentation.
 
 ## Tools