Description

When trying to record on a machine without an audio input device (e.g., Mac Studio with no external mic connected), the app shows a cryptic, unhelpful error message:

Failed to start recording: Failed to open recorder: Failed to fetch preferred config: A backend-specific error has occurred: An unknown error unknown to the coreaudio-rs API occurred

Expected Behavior

The app should show a clear, actionable error message telling the user that no microphone was found and suggesting they connect one.

Steps to Reproduce

1. Use Handy on a machine without a built-in microphone (e.g., Mac Studio) with no external mic connected
2. Trigger a recording
3. Observe the cryptic error toast

Environment

• Handy v0.7.12
• macOS (Mac Studio, no built-in mic)

Root Cause

The error originates from cpal/coreaudio-rs when attempting to get the preferred audio config for a device that doesn't exist. The backend doesn't perform a pre-flight check for available input devices, and the error classification only distinguishes "microphone_permission_denied" vs "unknown" — there's no "no_input_device" category.