Update skill docs/evals to short Docker tag scheme (latest-cu12 / latest-cu13)

Context

We are simplifying the published Docker image tags to add short cu<major> aliases (latest-cu12, latest-cu13, <version>-cu12/cu13) alongside the existing fully-qualified …-cuda<minor>-py<py> tags. The CI manifest publish (ci/docker/create_multiarch_manifest.sh), README.md, the docs install-selector, the NIM operator examples, and the gRPC docs have been updated to lead with the short tags.

The agent skills still reference the old nvidia/cuopt:latest-cuda12.9-py3.13 tag and should be updated to stay consistent (these go through the skill-evolution / CI validation flow, so tracking separately).

Files to update

Skill doc examples:

• skills/cuopt-install/SKILL.md (docker pull/run examples)
• skills/cuopt-server-api-python/SKILL.md (docker run example)
• skills/cuopt-install/references/verification_examples.md (docker run example)

Skill eval fixtures (ground-truth asserts the recommended tag):

• skills/cuopt-install/evals/evals.json
• skills/cuopt-install/benchmark/evals.json

Suggested change

Replace latest-cuda12.9-py3.13 (and similar) with latest-cu12 / latest-cu13. Update eval ground-truth and acceptance criteria so an agent following the new convention passes.

Note: short aliases only exist for releases built after the manifest change lands (26.6.0+).