docs(clients): add AgentDeck to Mobile clients

[mantou132]

Adds AgentDeck to the Mobile clients section.

AgentDeck is an Android app paired with a background daemon, agentdeckd, that runs on the user's computer. The daemon acts as an ACP client through the agent-client-protocol Rust crate and launches agents from the ACP registry: Claude Code, Codex, Cursor, GitHub Copilot, OpenCode, Qwen Code, Kimi CLI and others. The phone connects to the daemon by scanning a QR code. Traffic goes through an end-to-end encrypted relay, which users can also self-host.

From the app you can:

• create and load sessions
• switch config options
• answer permission requests
• browse files and Git changes
• get push notifications when a turn finishes

AgentDeck also includes a built-in free agent, based on OpenCode's free models, that works without a login.

• Repository: https://github.com/mantou132/AgentDeck
• Google Play: https://play.google.com/store/apps/details?id=com.mantou.agentdeck
• Scope: one documentation-only entry in docs/get-started/clients.mdx, inserted alphabetically

Validation

• npx prettier --check docs/get-started/clients.mdx