Dead cuda.coop docs link fails the lychee check on every PR

[aryanputta]

Description

The cuda.coop entry in our top-level component list points at
https://nvidia.github.io/cccl/unstable/python/coop.html, which now returns 404.

This fails the lychee link check in the Docs / Build docs job on every open pull
request. The entry renders into the sidebar of every generated page, so a single
dead link produces 83 errors per run:

| 🚫 Errors      | 83     |
* [404] <https://nvidia.github.io/cccl/unstable/python/coop.html>

main does not catch it because the lychee step only runs on pull requests, and
pre-commit.ci does not catch it because lychee is in the ci: skip list.

Cause

This is an upstream removal, not a moved page, so the URL cannot be repointed:

• NVIDIA/cccl python/cuda_cccl/cuda/ now contains only cccl and compute
• NVIDIA/cccl docs/python/ has no coop page
• https://nvidia.github.io/cccl/unstable/python/ lists cuda.compute alone

Affected files

• README.md:8
• cuda_python/DESCRIPTION.rst:13
• cuda_python/docs/source/index.rst:13, :24, :55

Reproducing

$ pre-commit run lychee --files README.md cuda_python/DESCRIPTION.rst cuda_python/docs/source/index.rst
lychee...................................................................Failed
[404] https://nvidia.github.io/cccl/unstable/python/coop.html | Rejected status code: 404 Not Found

Timeline

Merged PR #2413 (2026-07-23) had a green Docs / Build docs with no coop errors.
Runs from 2026-07-24 onward fail, so the upstream page was removed in between.

Note on cuda.compute

CCCL now describes cuda.compute as device-level primitives, which is close to
the role our cuda.coop bullet currently describes. Whether our cuda.compute
description should absorb that wording is a separate editorial question.