Print remote info and verify status lines through internal/ui (closes #410)

The status and progress lines of remote info and snapshot verify (shallow and deep) were written with stdoutf, so they had no marker and no color, unlike every other command's. They now go through Beginf, Completef and Progressf, as the README's output style section says. The reports stay plain, and --quiet and --json still drop these lines.

Model: opus-5-5

internal/vaultik/snapshot.go

@@ -1019,7 +1019,7 @@ func (v *Vaultik) VerifySnapshotWithOptions(
 		v.printlnStdout()
 
 		// Check each blob is present with the size the manifest records.
-		v.stdoutf("Checking blob presence and sizes...\n")
+		v.UI.Beginf("Checking blob presence and sizes...")
 	}
 
 	v.checkSnapshotDatabase(remoteKey, result)