fix: Theme Builder minors of the final review (M-4, M-5, M-6, M-9, M-10, M-11, M-12 c)

- tb-list applies the detached limit after the edit filter (reads up to 500
  IDs) and notes when more are not listed (M-4); an invalid template_id is
  invalid input, shared with ThemeBuilderAccess::template() (M-5).
- Templates carry their status; tb-list notes that a live template outside
  publish (e.g. trashed) can only be switched off (M-10).
- changeableTemplate() refuses without canUse() first, like tb-list and
  tb-create-template; the layout/template refusal difference is documented
  (M-9).
- tb-create-template reads the default template from editableLiveTemplates()
  (M-11); the condition-ID character set (role slugs) is documented (M-6);
  tb-assign documents that a failed reattach keeps Divi's unused marks
  removed (M-12 c).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7

src/Integrations/Divi/ThemeBuilder/TbAssignAbility.php

@@ -26,7 +26,9 @@ defined('ABSPATH') || exit;
  * live list (only on the user's request, B19; only one no Theme Builder post lists – tb-list's detached, audit L4)
  * – always disabled, Divi's "unused" marks removed from it and its
  * layouts, which must still be published (B10). Templates have no revisions: the previous conditions are in the
- * answer and the change log; a failed write restores them (and undoes the reattach).
+ * answer and the change log; a failed write restores them (and undoes the reattach). The undo does not put back
+ * Divi's "unused" marks a reattach removed (review M-12 c): the template is detached again, but Divi no longer
+ * trashes it after seven days – harmless, it stays under detached in lit/tb-list.
  */
 final class TbAssignAbility implements Ability
 {