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).

tests/widget-system/post-visual-contract.test.cjs

@@ -356,14 +356,42 @@ test('the pinned visual baseline records all source checksums', () => {
   }
 });
 
-test('single posts reserve a sidebar column only when its widget stack has content', () => {
+test('every scene reserves a sidebar column only when its widget stack has content', () => {
   const layout = read('inc/helpers/template-tags/site-layout.php');
   const single = read('inc/helpers/aksrt-single.php');
   const aside = read('inc/helpers/aksrt-single-aside.php');
+  const homepage = read('inc/helpers/homepage/content.php');
+  const sidebarTemplate = read('sidebar.php');
+  const archiveHelpers = read('inc/helpers/aksrt-archive.php');
+
+  // Single visibility decision: an empty widget stack collapses every scene
+  // (home/category/tag/search/page/archive) to no-sidebar, not just singles.
+  assert.match(layout, /if \(!aksrt_has_current_sidebar_widgets\(\)\) \{\s*return false;/);
+  assert.doesNotMatch(layout, /is_single\(\) && !aksrt_has_current_sidebar_widgets/);
+
+  // The resolver must answer home_sidebar before the is_page() branch so a
+  // static front page is checked against the zones the homepage renders.
+  const resolver = layout.match(/function aksrt_resolve_sidebar_id\(\): string \{[\s\S]*?\n\}/);
+  assert.ok(resolver, 'aksrt_resolve_sidebar_id should exist');
+  assert.ok(
+    resolver[0].indexOf('is_home() || is_front_page()') < resolver[0].indexOf('is_page()'),
+    'home/front_page branch must precede the is_page() branch'
+  );
 
-  assert.match(layout, /if \(is_single\(\) && !aksrt_has_current_sidebar_widgets\(\)\) \{\s*return false;/);
   assert.match(single, /\$show_aside = get_post_type\(\$post_id\) === 'post'[\s\S]*?&& aksrt_is_show_sidebar\(\);/);
   assert.match(aside, /get_post_type\(\$post_id\) !== 'post' \|\| empty\(\$ctx\['show_aside'\]\)/);
+
+  // Homepage aside renders under the same single decision; no dual gate.
+  assert.match(homepage, /function aksrt_homepage_render_sidebar\(\): void \{\s*if \(!aksrt_is_show_sidebar\(\)\) \{\s*return;/);
+  assert.doesNotMatch(homepage, /aksrt_homepage_has_sidebar/);
+
+  // Generic sidebar template early-returns instead of rendering an empty column.
+  assert.match(sidebarTemplate, /if \(!function_exists\('aksrt_is_show_sidebar'\) \|\| !aksrt_is_show_sidebar\(\)\) \{\s*return;/);
+  assert.doesNotMatch(sidebarTemplate, /legacy parity/);
+
+  // Archive helper takes only the page-level toggle; no dead params.
+  assert.match(archiveHelpers, /function aksrt_archive_has_sidebar\(bool \$enabled = true\): bool/);
+  assert.doesNotMatch(archiveHelpers, /preferred|wp_is_mobile/);
 });
 
 test('article visual matrix pins every breakpoint, state and strict threshold', () => {