Add multimodal embeddings support

[virgildotcodes]

Closes #308

Summary

Laravel AI currently only supports text inputs for embeddings, but provider APIs can accept richer media inputs. This PR adds multimodal embeddings input support and handles the provider-specific request shapes needed to send those inputs correctly.

This PR adds multimodal embeddings input support for embeddings, including:

• images
• audio
• documents
• video

It also validates unsupported provider / model combinations early, preserves the original media source when mapping embeddings inputs, and avoids fetching remote media when generating embeddings cache keys.

Examples

Gemini multimodal embeddings

use Laravel\Ai\Embeddings;
use Laravel\Ai\Files\Image;

$response = Embeddings::for([
    Image::fromPath('/path/to/image.png'),
])->generate(provider: 'gemini', model: 'gemini-embedding-2');

Voyage AI image embeddings

use Laravel\Ai\Embeddings;
use Laravel\Ai\Files\Image;

$response = Embeddings::for([
    Image::fromUrl('https://example.com/image.png'),
])->dimensions(1024)->generate(
    provider: 'voyageai',
    model: 'voyage-multimodal-3',
);

Voyage AI video embeddings

use Laravel\Ai\Embeddings;
use Laravel\Ai\Files\Video;

$response = Embeddings::for([
    Video::fromPath('/path/to/video.mp4'),
])->dimensions(1024)->generate(
    provider: 'voyageai',
    model: 'voyage-multimodal-3.5',
);

Changes

• widen embeddings inputs to accept text, images, audio, documents, and video
• add explicit validation for unsupported provider / input combinations
• route Gemini Embedding 2 and media embeddings requests through embedContent
• resolve Gemini provider-backed files to file URIs before sending embedding requests
• preserve remote, local, stored, and base64 media sources when converting embeddings inputs
• avoid remote fetches when building cache keys for remote embeddings inputs

Notes

• Gemini multimodal embeddings require gemini-embedding-2 or gemini-embedding-2-preview
• Voyage AI supports text and image embeddings with voyage-multimodal-3 or voyage-multimodal-3.5
• Voyage AI video embeddings require voyage-multimodal-3.5
• Voyage AI multimodal requests must use either URL media or base64 media exclusively

[pushpak1300]

can you fix merge conflicts ?

[virgildotcodes]

@pushpak1300 Done, and made some additional changes to support video on Voyage which is a new capability, and gemini-embedding-2 (release version) among other things.

[pushpak1300]

Thanks @virgildotcodes. I'll take a look.