26.8.0-trunk.162.0612.130428

runner-cleanup: give job-completed hook a .sh extension

The GitHub runner validates ACTIONS_RUNNER_HOOK_JOB_COMPLETED and rejects
it in the 'Complete runner' step unless the path ends in .sh/.ps1/.js:

  Error: /usr/local/sbin/runner-job-completed is not a valid path to a
  script. Make sure it ends in '.sh', '.ps1' or '.js'.

Rename runner-job-completed -> runner-job-completed.sh, install it under
that name, point the per-runner .env at it, and remove the old
extensionless copy from earlier installs. The .env wiring is an idempotent
sed, so re-running install migrates existing runners to the new path.

Signed-off-by: Igor Pecovnik <igor@armbian.com>