Add support for video urls correctly

[lws803]

I'm trying to videos to gemini 3 / gemini 2.5 flash models through Open Router ai sdk and have been encountering an issue:

File is not a PDF.

Taking a look at the code, https://github.com/OpenRouterTeam/ai-sdk-provider/blob/main/src/chat/convert-to-openrouter-chat-messages.ts#L110-L168 it seems we treat all video files as generic files instead of following the standard here from https://openrouter.ai/docs/guides/overview/multimodal/videos.

Are there any plans to add a case here for video support?

Additional info:
I'm on the latest package version 2.1.1