chore(ci): bump NVHPC to 26.5 (#6117)

* chore(ci): bump NVHPC to 26.5

Assisted-by: ClaudeCode:claude-opus-5

* chore(ci): download NVHPC deb with curl retries to dodge CDN 404s

Assisted-by: ClaudeCode:claude-fable-5

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Co-authored-by: Ralf W. Grosse-Kunstleve <rgrossekunst@nvidia.com>
1 file changed