Stop remote info counting a non-blob file under blobs/ (closes #295)

remote info counted every four-part key under blobs/ as a blob, while
prune skips a name that is not a blob hash. A stray file such as
.DS_Store was reported as an orphaned blob, with advice to run prune,
which then deleted nothing. remote info now takes its blob list from
prune's listAllRemoteBlobs, so its blob and orphan figures, in the
table and in --json, cover exactly what prune would consider.

blobKeyParts moves to prune.go, its only remaining user.

Model: opus-5-5

TODO.md

@@ -22,6 +22,14 @@ the tag exists and is exercised; what is left is merging `next` to
 
 # Completed Steps
 
+- 2026-10-13: Stopped `remote info` counting a file under `blobs/` that
+  is not a blob as an orphaned blob
+  ([issue #295](https://git.eeqj.de/sneak/vaultik/issues/295)). A stray
+  file such as `.DS_Store` was reported as an orphaned blob and the
+  report advised running `prune`, which skips such a file and deleted
+  nothing. `remote info` now takes its blob list from the same listing
+  `prune` uses, in the table and in `--json`.
+
 - 2026-10-12: Bound the local index to the destination an `s3.*` config
   names ([issue #298](https://git.eeqj.de/sneak/vaultik/issues/298)).
   Only `storage_url` was checked, so after `s3.bucket` or `s3.prefix`