Voice mode: auto-submit on Space release

Feature request

When using voice mode (hold Space to record), automatically submit the transcribed text when the Space bar is released, instead of requiring a separate action to commit/send.

Current behavior: After releasing Space, the transcribed text appears but requires manual confirmation to submit.

Desired behavior: Releasing Space both ends recording and auto-submits the transcribed message.

This would make voice interaction faster and more natural, especially for quick commands and iterative workflows.