Strip remaining FILE INFORMATION headers from all non-XML/README files

Removes DEFGROUP, INGROUP, PATH, VERSION, BRIEF metadata from:
- Root PHP files (index.php, custom.php, error.php, offline.php, component.php)
- Language INI files (en-GB, en-US)
- All index.html security stubs
- brand-showcase.html, theme-test.html

Copyright/SPDX block preserved in all files.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/language/en-US/tpl_mokocassiopeia.ini

@@ -1,17 +1,8 @@
-; Copyright (C) 2026 Moko Consulting <hello@mokoconsulting.tech>
+; Copyright (C) 2025 Moko Consulting <hello@mokoconsulting.tech>
 ;
 ; This file is part of a Moko Consulting project.
 ;
 ; SPDX-License-Identifier: GPL-3.0-or-later
-;
-; #FILE INFORMATION
-; DEFGROUP: Joomla.Template.Site
-; INGROUP: MokoCassiopeia
-; PATH: ./language/en-US/tpl_mokocassiopeia.ini
-; VERSION: 03.09.02
-; BRIEF: English (US) language strings for the MokoCassiopeia Joomla template
-;
-; Note: Template metadata strings (name, description) are in tpl_mokocassiopeia.sys.ini
 
 ; ===== System / layout =====
 TPL_MOKOCASSIOPEIA_DEVELOPMENTMODE_LABEL="Development Mode"