[doc-only] cuda.core: document how to install nightly (top-of-tree) builds

[matysanchez]

Closes #2166

What

Adds an Installing the latest nightly (top-of-tree builds) section to cuda_core/docs/source/install.rst. The section explains how to use gh run download to grab the wheel artifact from the most recent successful CI run on main, with notes for picking your Python version, target platform, and CUDA major version.

Why

Per the issue, the equivalent section already exists in numba-cuda-mlir. The two repos share CI infrastructure, so the recipe transfers directly — only repo name, workflow file (ci.yml), and artifact pattern names needed adapting.

Tested

• Verified gh run list -R NVIDIA/cuda-python -w ci.yml -b main -s success -L1 resolves cleanly against the live repo (returns the latest successful CI run).
• Pure additive change — no surrounding content modified. Indentation matches the surrounding RST blocks.

Verification

branch: hunter/issue-2166
files-changed: 1
commit: 6479b7f

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[matysanchez]

@leofang — when you have a moment, would you take a look? No rush.

I picked you based on merged 8 docs PRs in last 6 months; happy to address feedback or re-route to someone better if you're not the right person.

[matysanchez]

@mdboom — when you have a moment, would you take a look? No rush.

I picked you based on merged 8 docs PRs in last 6 months; happy to address feedback or re-route to someone better if you're not the right person.

[leofang]

Please do not ping individual team members. We'll triage PRs during team sync.

[matysanchez]

Thanks for the review, @leofang — pushed c4319d8 moving the section to be the first sub-subsection under Development environment, above Development with uv. Promoted the section underline from --- to ~~~ accordingly.

Also — sincere apology for the cold pings yesterday. I shouldn't have @-mentioned individual team members; I missed the team-triage workflow note. Won't happen again on cuda-python or other NVIDIA repos. Happy to close and resubmit without those comments if you'd prefer, but otherwise I'll just leave it for triage at your team's normal cadence.

[leofang]

Thanks, @matysanchez! If this PR is done, let's un-draft it!

[matysanchez]

@leofang thanks Leo