fix: show post-install listing in all execution paths and update error message

- Restructure stepPostInstall so command listing is shown for all modes
  that proceed to execute (interactive, dry-run, silent+allow-post-install)
- Update shellIdentifierRe error message to mention dots

Author: fullstackjam

internal/installer/installer.go

@@ -731,22 +731,22 @@ func stepPostInstall(cfg *config.Config) error {
 
 	commands := cfg.RemoteConfig.PostInstall
 
-	if cfg.DryRun {
-		// dry-run: show commands below without confirmation
-	} else if cfg.Silent || !system.HasTTY() {
+	if !cfg.DryRun && (cfg.Silent || !system.HasTTY()) {
 		if !cfg.AllowPostInstall {
 			ui.Warn("Skipping post-install script in silent mode (use --allow-post-install to enable)")
 			fmt.Println()
 			return nil
 		}
-	} else {
-		// Show commands before interactive confirmation
-		ui.Info(fmt.Sprintf("%d command(s) to run:", len(commands)))
-		for i, cmd := range commands {
-			fmt.Printf("  %d. %s\n", i+1, cmd)
-		}
-		fmt.Println()
+	}
+
+	// Show command listing for all modes that proceed (interactive, dry-run, silent+allowed)
+	ui.Info(fmt.Sprintf("%d command(s) to run:", len(commands)))
+	for i, cmd := range commands {
+		fmt.Printf("  %d. %s\n", i+1, cmd)
+	}
+	fmt.Println()
 
+	if !cfg.DryRun && !cfg.Silent && system.HasTTY() {
 		run, err := ui.Confirm("Run post-install script?", true)
 		if err != nil {
 			return err

internal/shell/shell.go

@@ -18,7 +18,7 @@ func validateShellIdentifier(value, label string) error {
 		return nil
 	}
 	if !shellIdentifierRe.MatchString(value) {
-		return fmt.Errorf("invalid %s: %q (only alphanumerics, hyphens, underscores allowed)", label, value)
+		return fmt.Errorf("invalid %s: %q (only alphanumerics, hyphens, underscores, dots allowed)", label, value)
 	}
 	return nil
 }