Keep local transcription when cancelling external provider processing

[jwadow]

When using a local transcription model with an external provider for post-processing, the local transcription may already be finished while the provider is still generating a response.

In that situation it would be nice to have a way to stop waiting for the provider without losing the local transcription. If I cancel the provider request, Handy could simply use the completed local result instead.

Another idea would be an optional timeout setting for the external provider. For example, if the provider doesn't respond within a user-defined time (like 10 seconds), Handy would automatically fall back to the local transcription.

The external provider is just an optional improvement, so it feels unnecessary to lose an already completed transcription just because the provider is slow or unresponsive.