feat: lit/tb-activate – the explicit switch, always a dry run first (answer F1)

- only _et_enabled; dry run in both directions lists conditions, exclusions,
  layouts, overlaps and possible overlaps (B9); confirm: true switches
- enabling needs conditions and published layouts (B10); a detached
  template needs reattach first; the default template is refused
- the off-switch reaches an attached, enabled template outside publish,
  e.g. in the trash (ruling Q16); result names the fast way back
- every switch in the change log; failed switch rolled back

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/Unit/Integrations/Divi/DiviIntegrationTest.php

@@ -78,7 +78,7 @@ final class DiviIntegrationTest extends TestCase
         self::assertSame('Divi Theme Builder', $group->label());
         self::assertFalse($group->isAvailable(), 'no Divi classes in unit tests');
         self::assertSame(
-            ['lit/tb-list', 'lit/tb-create-template', 'lit/tb-assign'],
+            ['lit/tb-list', 'lit/tb-create-template', 'lit/tb-assign', 'lit/tb-activate'],
             array_map(static fn (Ability $ability): string => $ability->name(), $group->abilities())
         );
         foreach ($group->abilities() as $ability) {