v0.6.4

Changed:
Fixed the Windows updater helper so it actually applies packaged updates instead of silently failing after Wisp closes.
Replaced brittle PowerShell Split-Path / Expand-Archive behavior with safer path handling and .NET zip extraction.
Changed update extraction to use a short temp folder to avoid Windows path-length failures in packaged builds.
Adjusted helper launch flags so the updater progress window and apply flow run reliably.
Added updater smoke tools that test both fake installs and real packaged install copies.
Fixed:
Settings could freeze/crash while opening the TTS/Kokoro section because CUDA detection imported ctranslate2 on the Qt UI thread.
CUDA auto-detection now uses nvidia-smi instead, avoiding heavy native ML imports during Settings startup.