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

tests/Support/ThemeBuilderFixtures.php

@@ -127,7 +127,11 @@ final class ThemeBuilderFixtures
         $store->allows('liveTemplates')->andReturn($templates);
         $store->allows('templateIds')->andReturn(array_map(static fn (Template $t): int => $t->id, $templates));
         $store->allows('template')->andReturnUsing(static fn (int $id): ?Template => $byId[$id] ?? null)->byDefault();
-        $store->allows('detachedIds')->andReturn(array_map(static fn (Template $t): int => $t->id, $detached));
+        $store->allows('detachedIds')->andReturnUsing(static fn (int $limit): array => array_slice(
+            array_map(static fn (Template $t): int => $t->id, $detached),
+            0,
+            $limit
+        ))->byDefault();
         $store->allows('isListedAnywhere')->andReturnUsing(
             static fn (int $id): bool => in_array($id, array_map(static fn (Template $t): int => $t->id, $templates), true)
         )->byDefault();