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

remote info counted every key under blobs/ with four or more path parts
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`.
+
 - 2026-10-13: Made `snapshot remove` fail for a snapshot that does not
   exist ([issue #293](https://git.eeqj.de/sneak/vaultik/issues/293)).
   The command never checked the ID: it reported the snapshot removed