refactor(js): complete push menu plugin overhaul (#5954)

- Single PushMenu instance instead of creating new ones per event
- Proper separation: setupSidebarBreakPoint() vs updateStateByResponsiveLogic()
- sidebar-open class only added on mobile (aligns with v3 behavior)
- Persistence now opt-in via data-enable-persistence="true"
- Config readable from data attributes on sidebar element
- Remove unused menusClose() and dead constants

BREAKING: enablePersistence defaults to false. Add
data-enable-persistence="true" to sidebar element to restore.

Based on PR #5954 by @dfsmania.

Co-Authored-By: Diego Smania <diego.smania@gmail.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: 3 people