Docs: name Bellows as another ACP client in IDE integration #30113

Disclosure: I work on Bellows, a free desktop app that runs coding agents over ACP.

What would you like to be added?

docs/ide-integration/index.md names JetBrains and Zed as ACP clients, with a short subsection each under "IDE-specific integration". Would you take a short Bellows subsection there (or just one line naming it, if you'd rather keep the list to editors)? Bellows is a desktop app for Windows, macOS and Linux; Gemini CLI is one of its built-in agents, and it lists every agent in the ACP Agent Registry.

Why is this needed?

People who want to run Gemini CLI in a desktop window rather than an editor have no pointer to a client that does that. Checked with Gemini CLI 0.66.0 and --acp.

Happy to open the PR once you say yes. If a third-party app isn't something you want on that page, just say so and I'll close this.