Replace HeatTreat_6.2.1.msi with HeatTreat_6-4-9.msi (ProductVersion
6.4.9.0, ProductCode {9E603EFE-888A-4E3F-8CF5-7F03B7029919}). The install
script globs HeatTreat*.msi so no logic change; the MSI's NOT
NEWERVERSIONDETECTED LaunchCondition makes 6.2.1 -> 6.4.9 a clean
in-place upgrade. Update version references in 02-Setup-HeatTreat.ps1.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>