[Bug]: a failed transcription shows the raw IPC error on the media card #968

Describe the bug

When transcription fails, the media card shows the raw IPC error string, which tells a user nothing about what went wrong:

Error invoking remote method 'stt:transcribe': Error: ffmpeg timed out after 60000ms on /Users/<user>/Downloads/<folder>/<file>.mp4

Steps to reproduce

1. Open a project whose media lives in ~/Downloads on a Mac where OpenScreen has not been granted access to that folder.
2. macOS raises its "access files in your Downloads folder" prompt; leave it unanswered for more than a minute. Transcription starts automatically and its ffmpeg waits on that prompt.

Expected

A short, human message on the card (the audio could not be read, check that OpenScreen can access the folder), without the Error invoking remote method wrapper.

Actual

The raw wrapper above, and "Generation failed, pick a language and regenerate". Regenerate works once the prompt is answered.

Environment

OpenScreen 2.0.0-rc.8, macOS 26.5.