Add optional Codex MCP control snippet

[omarelkhal]

Add optional Codex MCP control snippet

Published issue: #17

Parent

PRD: #13

What to build

Ship a Codex MCP configuration snippet that exposes the existing Aftertone MCP server from the install root. This is only for control commands such as status, set, restart, and repair; post-reply speech must still come from the Codex Stop hook.

Acceptance criteria

• Docs include a Codex MCP config snippet pointing at the install root py directory and python -m aftertone.mcp_server.
• The snippet is clearly optional and not required for speech.
• Docs state that MCP must not replace the Stop hook for post-reply audio.
• Any MCP parity gaps are linked to separate follow-up work instead of hidden in this slice.

Blocked by

• Codex guidance and per-chat control semantics #16