Fix the review findings in --help and config.example.yml

snapshot list says why a remote-only snapshot is listed by its remote
key. snapshot verify says what access to the destination it needs. The
note on the age-keygen file is two sentences in snapshot verify and
snapshot restore. remote nuke says "backup destination store".

config.example.yml names the commands that run without a snapshot.

Only help strings and comments change.

Model: fable-5-1

internal/cli/remote.go

@@ -41,9 +41,9 @@ func newRemoteNukeCommand() *cobra.Command {
 		Use:   "nuke",
 		Short: "Delete ALL snapshot metadata and blobs from the backup destination store",
 		Long: `Removes every snapshot's metadata, every blob and the destination
-marker from remote storage, and each removed snapshot from the local
-index. After this command completes successfully the bucket prefix is
-empty and the next backup starts from scratch.
+marker from the backup destination store, and each removed snapshot from
+the local index. After this command completes successfully the bucket
+prefix is empty and the next backup starts from scratch.
 
 This is destructive and irreversible. Requires --force, and permission
 to list and delete objects on the destination store.`,