[R][CI] r-binary-packages crossbow job fails for CRAN patch releases

[thisisnic]

Describe the bug, including details regarding any error messages, version, and platform.

The r-binary-packages crossbow job fails for CRAN patch releases (4-component versions like 23.0.1.1).

(This is all Claude diagnoses but looks right to me)

Root cause:

1. The binary build job extracts the version directly from DESCRIPTION and names files with the full version: r-libarrow-linux-x86_64-23.0.1.1.zip
2. The test job runs nixlibs.R which truncates the version to 3 components for releases (line 991: VERSION <- VERSION[1, 1:3])
3. The test job then looks for: r-libarrow-linux-x86_64-23.0.1.zip (missing the .1)
4. File not found → installation fails

Error from logs:

Error in download.file(from_url, to_file, quiet = hush, mode = "wb") :
  cannot open URL 'file:///__w/crossbow/crossbow/repo/libarrow/r-libarrow-linux-x86_64-23.0.1.zip', reason 'No such file or directory'

This was introduced in #45964 when migrating from jfrog to GitHub releases. The new naming scheme embeds the version directly in the filename, but the CI uses the full 4-component version while nixlibs.R truncates to 3 components for release versions.

Example failing run: https://github.com/ursacomputing/crossbow/actions/runs/23490124501

Component(s)

R