version promote --help says the current file is rewritten (closes #153)

The help text for `secret version promote` and a comment in
PromoteVersion said promote updates a "current symlink". `current` is a
plain file holding the version name, and promote rewrites it; the README
already says so. A new test runs `secret version promote --help` and
checks the output does not mention a symlink and does name the current
file.

Model: opus-5-5

internal/cli/version.go

@@ -64,7 +64,7 @@ func VersionCommands(cli *Instance) *cobra.Command {
 	promoteCmd := &cobra.Command{
 		Use:   "promote <secret-name> <version>",
 		Short: "Promote a specific version to current",
-		Long: "Updates the current symlink to point to the specified " +
+		Long: "Rewrites the secret's current file to name the specified " +
 			"version. The versions' own times are left unchanged; secret " +
 			"list then gives the time of the promote as the secret's last " +
 			"update.",
@@ -293,7 +293,7 @@ func (cli *Instance) PromoteVersion(
 			version, vault.ErrVersionNotFound, secretName)
 	}
 
-	// Update the current symlink using the proper function
+	// Rewrite the secret's current file to name the version
 	err = secret.SetCurrentVersion(cli.fs, secretDir, version)
 	if err != nil {
 		return fmt.Errorf("failed to update current version: %w", err)