`LanguageModelChatInformation#capabilities` should be optional

[jrieken]

All properties of LanguageModelChatCapabilities are optional and hence it would be nice/better to also make LanguageModelChatInformation#capabilities optional. Today, authors need to spell out an empty object if all capabilities are lacked, like so

{
	id: 'b',
	family: 'b',
	capabilities: {

	},
	maxInputTokens: 100,
	maxOutputTokens: 1000,
	name: 'b-modelOptions',
	vendor: 'b',
	version: '1',
	isUserSelectable: true,
	isDefault: true
}

[lramos15]

We made this decision on purpose during the API sync because we wanted to force users to look into the capabilities and give it some intentional thought so that they weren't accidentally overlooked and not set

cc @mjbvz

[mjbvz]

Yes the thinking was that capabilities such as toolCalling are important for most models and easy to miss if capabilities is optional. We wanted to encourage extension authors to at least consider the capabilities object