Both update cue variants ("update 1.wav" / "update 2.wav") replaced with a
gentler mix that signals an incoming update without interrupting work mid-flow.
About-box note added (tidied wording); csproj <Version> bumped to 4.3.1. No code
changes.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>