RunWithOutput and RunWithOutputs each carried their own near-identical
copy of the index.lock retry loop. Extract the loop into a single
retryOnLockError helper so the retry policy lives in one place, ahead of
changing that policy. Behavior is unchanged; the added tests characterize
it (success and non-lock errors run once, a lock error in the output is
retried).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
e90daaf812