Convert the procedural hooks to OOP hook classes in the Vartheme BS5 theme

Problem/Motivation

The Vartheme BS5 theme implements its hooks as procedural functions in vartheme_bs5.theme. Drupal 11 provides object-oriented hooks via the #[Hook] attribute (change record), which are autoloaded and support dependency injection. Themes support OOP hook classes as of Drupal 11.2.

Steps to reproduce

Review vartheme_bs5.theme: the alter/registration hooks are procedural functions.

Proposed resolution

Move the convertible procedural hook implementations (hook_theme, hook_library_info_alter, hook_form_alter) into an object-oriented hook class Drupal\vartheme_bs5\Hook\VarthemeBs5Hooks using the #[Hook] attribute, with the theme extension list injected via the constructor. The many preprocess hooks and the vartheme_bs5_process_menu_level() helper are kept procedural in the .theme file.

Remaining tasks

• ✅ Add src/Hook/VarthemeBs5Hooks.php
• ✅ Clean vartheme_bs5.theme (keep preprocess + helper)
• ➖ Keep preprocess hooks procedural
• ❌ Reviewed by a human

User interface changes

None.

API changes

None. These are standard theme hooks invoked by core only; see the OOP hooks change record.

Data model changes

None.

Release notes snippet

Converted the Vartheme BS5 procedural hook_theme, hook_library_info_alter and hook_form_alter implementations to a Drupal 11 object-oriented hook class.