v3.0.10-beta.9

mimic — a thrown-away custom voice download leaves no empty file

The cleanup removed the file before its stream had finished opening, so the
open could recreate it empty (a 1-in-3 failure of the over-the-limit test).
The file is now removed once the stream has closed.

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Windows installer — not code-signed (SmartScreen → More info → Run anyway). Bundles its own Node runtime; auto-updates in place via electron-updater, no re-download.