The filesystem blob store fails to list or delete blobs that are deleted concurrently

listDescendants uses Files.walk. A directory deleted during the walk, by another thread or another cluster member on a shared directory, throws UncheckedIOException(NoSuchFileException) from the stream and aborts the whole listing; hasDescendants is affected too. deleteDescendants uses PathUtils.deleteDirectory, whose visitor rethrows NoSuchFileException for a directory removed during the walk.

Expected: blobs that disappear during a listing are skipped, and deleting something already gone is not an error (idempotent deletion, documented in the BlobStore javadoc).

Possible fix: an own FileVisitor whose visitFileFailed continues on NoSuchFileException, and a missing root treated as empty. The listing failure was reproduced with a plain JDK test; the deletion failure comes from reading the commons-io code.