Add Code Assistant link to agents overview

Author: stippi

docs/overview/agents.mdx

@@ -8,6 +8,7 @@ The following agents can be used with an ACP Client:
 - [Augment Code](https://docs.augmentcode.com/cli/acp)
 - [Claude Code](https://docs.anthropic.com/en/docs/claude-code/overview) (via [Zed's SDK adapter](https://github.com/zed-industries/claude-code-acp))
 - [Codex CLI](https://developers.openai.com/codex/cli) (via [Zed's adapter](https://github.com/zed-industries/codex-acp))
+- [Code Assistant](https://github.com/stippi/code-assistant?tab=readme-ov-file#configuration)
 - [Docker's cagent](https://github.com/docker/cagent)
 - [Gemini CLI](https://github.com/google-gemini/gemini-cli)
 - [Goose](https://block.github.io/goose/docs/guides/acp-clients)