Docs updates September (#38796)

Closes #ISSUE

Release Notes:

- N/A

---------

Co-authored-by: Katie Geer <katie@zed.dev>
Co-authored-by: Marshall Bowers <git@maxdeviant.com>
Co-authored-by: David Kleingeld <davidsk@zed.dev>

docs/src/ai/external-agents.md

@@ -5,6 +5,8 @@ Zed supports terminal-based agents through the [Agent Client Protocol (ACP)](htt
 Currently, [Gemini CLI](https://github.com/google-gemini/gemini-cli) serves as the reference implementation.
 [Claude Code](https://www.anthropic.com/claude-code) is also included by default, and you can [add custom ACP-compatible agents](#add-custom-agents) as well.
 
+Zed's affordance for external agents is strictly UI-based; the billing and legal/terms arrangement is directly between you and the agent provider. Zed does not charge for use of external agents, and our [zero-data retention agreements/privacy guarantees](./ai-improvement.md) are **_only_** applicable for Zed's hosted models.
+
 ## Gemini CLI {#gemini-cli}
 
 Zed provides the ability to run [Gemini CLI](https://github.com/google-gemini/gemini-cli) directly in the [agent panel](./agent-panel.md).