fix(sidebar): collapse empty sidebar column on every scene

Sidebar visibility had two disconnected decisions: the body site-layout-*
class (via aksrt_is_show_sidebar_filter) only checked widget activity for
singles, while the homepage aside renderer skipped the column and
sidebar.php rendered an empty one. With the toggle on and no widgets, the
homepage kept a reserved gutter and squeezed the main content aside.

- collapse every scene to no-sidebar when the sidebar widget stack is empty
- resolve home_sidebar before the page branch so a static front page is
  checked against the zones the homepage renders
- guard the homepage aside with aksrt_is_show_sidebar() alone and drop the
  duplicate aksrt_homepage_has_sidebar gate
- early-return sidebar.php instead of rendering an empty column
- drop dead code: archive helper $preferred param, wp_is_mobile fallback,
  container--no-sidebar class, unreachable front-page fallback
- update post-visual-contract to pin the single visibility decision

Verification: php -l on all changed files; node --test
tests/widget-system/*.test.cjs 242/243 (the toast-contract failure is
pre-existing and unrelated).

tag.php

@@ -27,7 +27,7 @@ $archive_settings = class_exists('\AKSRT\Core\TermMeta')
 	];
 
 $has_sidebar = function_exists('aksrt_archive_has_sidebar')
-	? aksrt_archive_has_sidebar('tag_sidebar', !empty($archive_settings['show_sidebar']))
+	? aksrt_archive_has_sidebar(!empty($archive_settings['show_sidebar']))
 	: (!empty($archive_settings['show_sidebar']) && is_active_sidebar('tag_sidebar'));
 $description = !empty($archive_settings['show_desc']) ? wp_kses_post((string) $archive_settings['description']) : '';
 $header_style = (string) $archive_settings['header_style'];