#16597: media: skip binary application attachments in file extraction

## Summary - treat binary application MIME families (including `application/vnd.*`, archive-like `application/x-*`, and `application/octet-stream`) as non-inlineable in media understanding - keep text-like MIME handling intact for explicit text extensions while preventing Office/archive blobs from entering prompt context - add regression coverage for vnd, x-archive, and octet-stream payloads ## Issue - Fixes #16513