[Platform][Mistral] Add support for Voxtral models with audio input and tool-calling

[avhulst]

Q	A
Bug fix?	no
New feature?	Yes
Docs?	no
Issues	--
License	MIT

This pull request extends the Mistral integration to add support for the VOXTRAL models, which are specialized for processing audio data. This enables the transcription of audio files through the Mistral platform.

Key Changes:

• New Model Constants: In the Mistral class, the constants VOXTRAL_SMALL and VOXTRAL_MINI have been added.
• Audio Capability: The Capability::INPUT_AUDIO is now correctly assigned to the models when one of the VOXTRAL models is selected.
• Usage Example: A new ai:mistral command has been created to demonstrate the functionality. It shows how to send an audio file (audio.mp3) to the VOXTRAL_SMALL model for transcription.

Usage Example (AiMistralCommand.php):

// ...

// Select the VOXTRAL_SMALL model
$model = new Mistral(Mistral::VOXTRAL_SMALL);

// ...

// Call the agent with a system message and an audio file as user input
$messages = new MessageBag(
    Message::forSystem('You are an assistant for audio transcriptions.'),
    Message::ofUser(
        'Please give me the content of the audio file',
        Audio::fromFile(dirname(__DIR__, 2).'/audio.mp3'),
    ),
);

$result = $agent->call($messages)->getContent();

// ...

[OskarStark]

Thanks @avhulst for working on this feature, this is much appreciated.