test(mcp): assert wire-format type field in tool serialization test

The SDK's constant.Function auto-marshals zero to "function", but
having an explicit wire-format assertion proves this contract holds.

Signed-off-by: asaadbalum <asaad.balum@gmail.com>

Author: asaadbalum

src/semantic-router/pkg/mcp/types_test.go

@@ -37,6 +37,7 @@ func TestConvertToolToOpenAI_BasicTool(t *testing.T) {
 	var parsed map[string]interface{}
 	require.NoError(t, json.Unmarshal(body, &parsed))
 
+	assert.Equal(t, "function", parsed["type"])
 	fn := parsed["function"].(map[string]interface{})
 	assert.Equal(t, "get_weather", fn["name"])
 	params := fn["parameters"].(map[string]interface{})