Summary

Raise a user-facing error when an audio recording URL is not accessible, instead of silently treating it as text.

Problem

When external audio URLs return 403/inaccessible, detect_input_type() returns 'file'. Since 'file' is not in _SUPPORTED_MEDIA, the URL passes through as plain text to the LLM — producing meaningless eval results.

Fix

In the shared media detection path (llm_payloads.py), when type is 'file' and URL has an audio extension (.wav, .mp3, etc.), raise:

"Audio recording is not accessible for '{key}'. The file could not be downloaded — please ensure the recording URL is valid and accessible."

Test plan

• Pass an inaccessible audio URL → error raised with friendly message
• Pass an accessible audio URL → processed as audio normally
• Pass a non-audio URL that returns 403 → no error (only audio extensions trigger it)