[BUG] Error processing Latex .tex files during chat

[DLM-unipd]

🐞Describe the bug

During a chat, uploading a Latex file with extension .tex is allowed, but it's causing an error "Failed to run stream handler: An error occurred (ValidationException) when calling the ConverseStream operation: Document format is required.".
Renaming the file with ".txt" is not solving the problem, it's causing another MIME error: "Failed to run stream handler: An error occurred (ValidationException) when calling the ConverseStream operation: Unsupported MIME type: application/x-tex. Retry your request with a supported file type: xlsx, txt, pdf, csv, md, doc, html, xls, docx".

const TEXT_FILE_EXTENSIONS in frontend/src/constants/supportedAttachedFiles.ts provides .tex as an allowed extension for text file.

🔄 To Reproduce

Steps to reproduce the behavior:

1. Go to new chat using for instance Claude Sonnet 4.6
2. Upload a Latex file (.tex)
3. Ask something (send request)
4. A "Failed to run stream handler: An error occurred (ValidationException) when calling the ConverseStream operation: Document format is required." shows up.

📷 Screenshots