Remove the #[LegacyHook] shims for full OOP hooks in the Vartheme BS4 theme

Problem/Motivation

The Vartheme BS4 hooks already live in the OOP Drupal\vartheme_bs4\Hook\VarthemeBs4Hooks class, but vartheme_bs4.theme still keeps #[LegacyHook] backward-compat shims that delegate to that class. For Drupal ~11.4.0 these standard theme hooks are invoked by core only, so the shims are redundant.

Steps to reproduce

Review vartheme_bs4.theme: every function is a #[LegacyHook] shim delegating to Drupal\vartheme_bs4\Hook\VarthemeBs4Hooks.

Proposed resolution

Remove the #[LegacyHook] shims and delete vartheme_bs4.theme; all hook logic already lives in the OOP #[Hook] class (change record).

Remaining tasks

• ✅ File an issue about this project
• ✅ Addition/Change/Update/Fix to this project
• ✅ Testing to ensure no regression
• ➖ Automated unit/functional testing coverage
• ➖ Developer Documentation support on feature change/addition
• ➖ User Guide Documentation support on feature change/addition
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ✅ Reviewed by a human
• ✅ Code review by maintainers
• ✅ Full testing and approval
• ✅ Credit contributors
• ✅ Review with the product owner
• ✅ Update Release Notes
• ✅ Release varbase-9.2.0, vartheme_bs4-9.2.0

User interface changes

• N/A

API changes

• The #[LegacyHook] procedural shim functions are removed; the logic remains available on the OOP hook class service. Standard theme hooks invoked by core only.

Data model changes

• N/A

Release notes snippet

• task: #3608379 Remove the #[LegacyHook] shims for full OOP hooks