docs/tests: standardize test header and correct manifest-contract notes

- Use the full license header (from the plugin's own setup.php) in
  tests/Unit/PruneFilesTest.php instead of the abbreviated copyright banner.
- Document that the manifest drift check and the upgrade-time prune also
  handle phpunit.xml and .md* files, matching the implemented behavior.

Author: Copilot

.github/copilot-instructions.md

@@ -176,4 +176,4 @@ existing code or adding new code, not just in dedicated cleanup passes:
 
 ## File manifest & upgrade pruning
 
-The plugin ships a root `manifest.json` with three arrays: `tombstones` (files/directories older versions shipped that have since moved or been removed), `expected` (the top-level files and directories that ship today, directories written with a trailing `/`), and `whitelist` (paths holding user data that must never be touched). Keep `expected` current: CI runs `tests/bin/validate-manifest.php`, which fails on any drift between `expected` and the real top-level tree (it ignores `tests/`, `.git*`, and whitelisted paths). Custom customer CSS/theme files belong in `expected`, and stylesheets live in `css/` (not `themes/`). On upgrade, `plugin_quicktree_prune_files()` deletes the tombstoned paths and the dev-only `tests/` tree, leaves `whitelist` and `.git*` alone, and logs (without removing) any top-level entry the manifest does not account for. As a safety measure it refuses any tombstone that resolves outside the plugin directory (a tampered manifest.json) and logs a warning for any file or directory it cannot remove. When you move or delete a shipped file, add its old path to `tombstones` and update `expected` in the same change.
+The plugin ships a root `manifest.json` with three arrays: `tombstones` (files/directories older versions shipped that have since moved or been removed), `expected` (the top-level files and directories that ship today, directories written with a trailing `/`), and `whitelist` (paths holding user data that must never be touched). Keep `expected` current: CI runs `tests/bin/validate-manifest.php`, which fails on any drift between `expected` and the real top-level tree (it ignores `tests/`, `phpunit.xml`, `.git*`, `.md*`, and whitelisted paths). Custom customer CSS/theme files belong in `expected`, and stylesheets live in `css/` (not `themes/`). On upgrade, `plugin_quicktree_prune_files()` deletes the tombstoned paths, the dev-only `tests/` tree, and the `phpunit.xml` test config, leaves `whitelist`, `.git*`, and `.md*` alone, and logs (without removing) any top-level entry the manifest does not account for. As a safety measure it refuses any tombstone that resolves outside the plugin directory (a tampered manifest.json) and logs a warning for any file or directory it cannot remove. When you move or delete a shipped file, add its old path to `tombstones` and update `expected` in the same change.

tests/Unit/PruneFilesTest.php

@@ -1,7 +1,25 @@
 <?php
 /*
  +-------------------------------------------------------------------------+
+ | Copyright (C) 2004-2022 Howard Jones                                    |
  | Copyright (C) 2004-2026 The Cacti Group                                 |
+ |                                                                         |
+ | This program is free software; you can redistribute it and/or           |
+ | modify it under the terms of the GNU General Public License             |
+ | as published by the Free Software Foundation; either version 2          |
+ | of the License, or (at your option) any later version.                  |
+ |                                                                         |
+ | This program is distributed in the hope that it will be useful,         |
+ | but WITHOUT ANY WARRANTY; without even the implied warranty of          |
+ | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the           |
+ | GNU General Public License for more details.                            |
+ +-------------------------------------------------------------------------+
+ | Cacti: The Complete RRDtool-based Graphing Solution                     |
+ +-------------------------------------------------------------------------+
+ | This code is designed, written, and maintained by the Cacti Group. See  |
+ | about.php and/or the AUTHORS file for specific developer information.   |
+ +-------------------------------------------------------------------------+
+ | http://www.cacti.net/                                                   |
  +-------------------------------------------------------------------------+
 */