Check behavior of a server with just tools.

Fixed bugs:
- "tools/list" can have missing params
- "_meta" should not be nil
- empty resource or prompts should not be returned as 'null'
- the server should not crash when params are passed to tools/call
- missing required input fields should be rejected (#449)
- output and input should be validated against their actual json, not Go
	representation
- When arguments are missing, the request should succeed if all properties are
	optional, and observe any default values.

-- tools --
greet
structured
tomorrow
inc

-- 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": 3, "method": "resources/list" }
{ "jsonrpc": "2.0", "id": 4, "method": "prompts/list" }
{ "jsonrpc": "2.0", "id": 5, "method": "tools/call" }
{ "jsonrpc": "2.0", "id": 6, "method": "tools/call", "params": {"name": "greet", "arguments": {"Name": "you"} } }
{ "jsonrpc": "2.0", "id": 1, "result": {} }
{ "jsonrpc": "2.0", "id": 7, "method": "tools/call", "params": {"name": "structured", "arguments": {"In": "input"} } }
{ "jsonrpc": "2.0", "id": 8, "method": "tools/call", "params": {"name": "structured", "arguments": {} } }
{ "jsonrpc": "2.0", "id": 9, "method": "tools/call", "params": {"name": "tomorrow", "arguments": { "Now": "2025-06-18T15:04:05Z" } } }
{ "jsonrpc": "2.0", "id": 10, "method": "tools/call", "params": {"name": "greet" } }
{ "jsonrpc": "2.0", "id": 11, "method": "tools/call", "params": {"name": "inc", "arguments": { "x": 3 } } }
{ "jsonrpc": "2.0", "id": 11, "method": "tools/call", "params": {"name": "inc" } }

-- server --
{
	"jsonrpc": "2.0",
	"id": 1,
	"result": {
		"capabilities": {
			"logging": {},
			"tools": {
				"listChanged": true
			}
		},
		"protocolVersion": "2024-11-05",
		"serverInfo": {
			"name": "testServer",
			"version": "v1.0.0"
		}
	}
}
{
	"jsonrpc": "2.0",
	"id": 2,
	"result": {
		"tools": [
			{
				"description": "say hi",
				"inputSchema": {
					"type": "object",
					"required": [
						"Name"
					],
					"properties": {
						"Name": {
							"type": "string"
						}
					},
					"additionalProperties": false
				},
				"name": "greet"
			},
			{
				"inputSchema": {
					"type": "object",
					"properties": {
						"x": {
							"type": "integer",
							"default": 6
						}
					},
					"additionalProperties": false
				},
				"name": "inc",
				"outputSchema": {
					"type": "object",
					"required": [
						"y"
					],
					"properties": {
						"y": {
							"type": "integer"
						}
					},
					"additionalProperties": false
				}
			},
			{
				"inputSchema": {
					"type": "object",
					"required": [
						"In"
					],
					"properties": {
						"In": {
							"type": "string",
							"description": "the input"
						}
					},
					"additionalProperties": false
				},
				"name": "structured",
				"outputSchema": {
					"type": "object",
					"required": [
						"Out"
					],
					"properties": {
						"Out": {
							"type": "string",
							"description": "the output"
						}
					},
					"additionalProperties": false
				}
			},
			{
				"inputSchema": {
					"type": "object",
					"required": [
						"Now"
					],
					"properties": {
						"Now": {
							"type": "string"
						}
					},
					"additionalProperties": false
				},
				"name": "tomorrow",
				"outputSchema": {
					"type": "object",
					"required": [
						"Tomorrow"
					],
					"properties": {
						"Tomorrow": {
							"type": "string"
						}
					},
					"additionalProperties": false
				}
			}
		]
	}
}
{
	"jsonrpc": "2.0",
	"id": 3,
	"result": {
		"resources": []
	}
}
{
	"jsonrpc": "2.0",
	"id": 4,
	"result": {
		"prompts": []
	}
}
{
	"jsonrpc": "2.0",
	"id": 5,
	"error": {
		"code": -32600,
		"message": "invalid request: missing required \"params\""
	}
}
{
	"jsonrpc": "2.0",
	"id": 1,
	"method": "ping"
}
{
	"jsonrpc": "2.0",
	"id": 6,
	"result": {
		"content": [
			{
				"type": "text",
				"text": "hi you"
			}
		]
	}
}
{
	"jsonrpc": "2.0",
	"id": 7,
	"result": {
		"content": [
			{
				"type": "text",
				"text": "{\"Out\":\"Ack input\"}"
			}
		],
		"structuredContent": {
			"Out": "Ack input"
		}
	}
}
{
	"jsonrpc": "2.0",
	"id": 8,
	"error": {
		"code": -32602,
		"message": "invalid params: validating \"arguments\": validating root: required: missing properties: [\"In\"]"
	}
}
{
	"jsonrpc": "2.0",
	"id": 9,
	"result": {
		"content": [
			{
				"type": "text",
				"text": "{\"Tomorrow\":\"2025-06-19T15:04:05Z\"}"
			}
		],
		"structuredContent": {
			"Tomorrow": "2025-06-19T15:04:05Z"
		}
	}
}
{
	"jsonrpc": "2.0",
	"id": 10,
	"error": {
		"code": -32602,
		"message": "invalid params: validating \"arguments\": validating root: required: missing properties: [\"Name\"]"
	}
}
{
	"jsonrpc": "2.0",
	"id": 11,
	"result": {
		"content": [
			{
				"type": "text",
				"text": "{\"y\":4}"
			}
		],
		"structuredContent": {
			"y": 4
		}
	}
}
{
	"jsonrpc": "2.0",
	"id": 11,
	"result": {
		"content": [
			{
				"type": "text",
				"text": "{\"y\":7}"
			}
		],
		"structuredContent": {
			"y": 7
		}
	}
}