`docker-mcp` v0.28.0 is broken with OpenAI

[dgageot]

Starting from v0.28.0, any query sent to OpenAI will fail because one of the gateway's default tool (mcp-config-set) has an invalid schema that's rejected by OpenAI backend.

How to reproduce:

curl https://api.openai.com/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $OPENAI_API_KEY" \
  -d "$(cat <<EOF
{
    "model": "gpt-4o-mini",
    "tools": [{
        "type": "function",
        "function": {
            "name": "say_hello",
            "description": "Return a friendly greeting",
            "parameters": $(docker mcp tools inspect --format=json mcp-config-set | jq .inputSchema)
        }
    }],
    "messages": [
      {"role": "user", "content": "Say hi"}
    ]
  }
EOF
)"