document compatibility workarounds

README.md

@@ -103,6 +103,15 @@ database; its temporary data is discarded when the container stops.
 This project uses several old dependencies, so a few small compatibility fixes
 are included:
 
+Temporary workarounds and legacy runtime pins are marked `TODO(compat)` in the
+source, with the condition for removing or replacing each one. Search for this
+marker during upgrades. In particular, remove the test `artisan()` override once
+Laravel's inherited helper works, and remove both the package-manifest patch
+and its Composer hook once Laravel supports Composer 2 directly.
+
+The test startup timestamp, isolated database settings, and database safety
+check are normal test infrastructure, not temporary version workarounds.
+
 - `phpdocumentor/phpdocumentor` 2.* was removed from `require-dev`. It requires
   Symfony 2.x, conflicts with Laravel 5.6, and was never present in
   `composer.lock`.