ELOOP raised while resolving the caller-selected path (access/realpath)
is a symbolic link loop or over-deep chain in that path, not evidence of
a change. Classify filesystem failures by resolution stage so only ELOOP
from opening the canonical path with symbolic links rejected keeps the
"target changed while being opened" reason. The structured code,
category and retryability are unchanged.
Fixes#5521
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
