Issue a warning message when a voice name in the TTS config XML does not match an available voice.

Note that such mismatches are allowed and are currently silently ignored because one may want to always use the same configuration file, even if certain engines are not available, or some voices of an engine are not available for some reason.

So perhaps this behavior should be optional?

Start by locating the TTS configuration handling and the code that resolves configured voice names against available voices. Determine how an optional warning should be enabled while preserving silently ignored mismatches, then verify that both matching and unavailable voices behave as intended.

Written by the indexing model from the issue text.