Every boot after the migration completes logged
`WARN legacy sidecar directory could not be removed / No such file or
directory`. The directory being absent IS the end state — it is what
success looks like from the second boot onward — so this warned about
the migration having worked, forever, on every restart.
Returns early when the root is gone, which also skips walking three
directories that no longer exist. The remaining `Err` arms keep their
warning for the cases that are genuinely failures: a directory that
exists and cannot be removed or moved aside.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Edouard Vanbelle
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