Check behavior of a server with just prompts.

Fixed bugs:
- Empty tools lists should not be returned as 'null'.
- No params in 'prompts/get' should not panic.

-- prompts --
code_review

-- client --
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "initialize",
  "params": {
    "protocolVersion": "2024-11-05",
    "capabilities": {},
    "clientInfo": { "name": "ExampleClient", "version": "1.0.0" }
  }
}
{ "jsonrpc":"2.0", "method": "notifications/initialized" }
{ "jsonrpc": "2.0", "id": 2, "method": "tools/list" }
{ "jsonrpc": "2.0", "id": 4, "method": "prompts/list" }
{ "jsonrpc": "2.0", "id": 5, "method": "prompts/get" }

-- server --
{
	"jsonrpc": "2.0",
	"id": 1,
	"result": {
		"capabilities": {
			"logging": {},
			"prompts": {
				"listChanged": true
			}
		},
		"protocolVersion": "2024-11-05",
		"serverInfo": {
			"name": "testServer",
			"version": "v1.0.0"
		}
	}
}
{
	"jsonrpc": "2.0",
	"id": 2,
	"result": {
		"tools": []
	}
}
{
	"jsonrpc": "2.0",
	"id": 4,
	"result": {
		"prompts": [
			{
				"arguments": [
					{
						"name": "Code",
						"required": true
					}
				],
				"description": "do a code review",
				"name": "code_review"
			}
		]
	}
}
{
	"jsonrpc": "2.0",
	"id": 5,
	"error": {
		"code": -32600,
		"message": "invalid request: missing required \"params\""
	}
}
