Wire up remaining placeholder settings, implement menu search (v2.4.0)

- Custom dashboard, Modern plugins page, and Modern comments page
  toggles previously had no effect at all — their respective takeovers/
  redirects (DashboardTakeover, SubApps' Plugins/Comments handling,
  MenuSerializer's link rewrites) ran unconditionally regardless of the
  setting. All three now default to their previous always-on behavior
  but can actually be turned off.
- Menu search had zero implementation. Sidebar.vue now shows a real
  search box (gated on the setting) that filters both the WP-native menu
  and the Aurora nav section by title, auto-expanding matching sections.
- Removed "Modern posts table" and "Modern users page" toggles (and
  their now-empty Posts/Users settings categories) — both described a
  custom management page that was never built. A checkbox with nothing
  behind it is worse than no checkbox.

Verified all four live: dashboard/plugins/comments toggles correctly
flip between the Aurora and native experience and back; menu search
filters correctly and clears back to the full menu.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

CHANGELOG.md

@@ -5,6 +5,30 @@ version bump. Starts at 2.1.0 — earlier history (the theming rebuild,
 window chrome/taskbar, Site Editor support, etc.) lives in `git log` and
 `PROJECT_STATUS.md`, not reconstructed here.
 
+## [2.4.0] - 2026-07-04
+
+### Added
+- Settings > Menu's "Menu search" toggle now actually does something —
+  previously had no implementation at all. Shows a real search box at the
+  top of the sidebar that filters both the WP-native menu list and the
+  Aurora nav section by title, auto-expanding every section with a match.
+
+### Fixed
+- Settings > Dashboard's "Custom dashboard" toggle now actually gates the
+  dashboard takeover — previously the Aurora dashboard always replaced the
+  native one regardless of this setting, with no way to turn it back off.
+- Settings > Plugins' "Modern plugins page" and Settings > Comments'
+  "Modern comments page" toggles now actually gate their respective
+  takeovers/redirects the same way — previously both ran unconditionally
+  regardless of these settings.
+
+### Removed
+- Settings > Posts' "Modern posts table" and Settings > Users' "Modern
+  users page" toggles — both described a custom management interface that
+  was never built. Shipping a checkbox with nothing behind it is worse
+  than not having the checkbox; removed rather than left as dead UI. Their
+  categories are removed too, since they had no other fields.
+
 ## [2.3.1] - 2026-07-04
 
 ### Fixed