Discussed in #29576 (comment), for now we need to remember to unset "CUDA CI" label and set it again manually on automated array API lock-file PRs like #29766.

From #29576 (comment), maybe this is due to triggering a workflow from a workflow limitations, see doc. Apparently you need a PAT rather than the default GITHUB_TOKEN when you are in this case. The last example in the doc is very similar to our use case I think:

Conversely, the following workflow uses GITHUB_TOKEN to add a label to an issue. It will not trigger any workflows that run when a label is added.

I don't remember if we have a PAT for some of the CI that we could try to see whether that fixes the issue ...