get-dxc.ps1 fetched releases/latest with no pin or hash, so the compiler that
defines parity could change under the tests. It now downloads v1.9.2607's
dxc_2026_07_29.zip (dxcompiler 1.9.0.5402) and refuses a zip whose SHA256 is
not A1DFB116...CD241. The hash was taken from the zip downloaded from
Microsoft's GitHub release and matches the digest GitHub publishes for the
asset. Script ran end to end and installed 1.9.0.5402.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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