fix(creator-studio): caret overlap in toolbar and hidden sub-categories

工具条下拉触发器的下三角原本绝对定位在按钮右下角，按钮宽度不够时会压到
居中的文字上。改为文字 + 三角同行排版（.jio-creator__tool-meta），宽度不足
时只压缩文字。

分类只查询 parent=0，导致二级 / 三级分类在投稿页完全不可选。新增
SubmitCategories 统一解析：
- 取全部分类并按父子关系深度优先展平，带上 depth / path；
- 白名单按"选了上级即包含其全部子级"展开，未配置白名单时不做额外过滤；
- 创作者工作台、经典投稿表单、保存校验与审核应用共用同一份结果。

选择器按 depth 缩进，搜索同时匹配完整路径。

同时把 assets/creator-studio/build 与 assets/admin/build 统一为整目录忽略
（不再跟踪 .gitkeep），避免构建产物反复被误提交。

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/widget-system/creator-studio-contract.test.cjs

@@ -380,7 +380,6 @@ test('quote, hidden content, and block math render like the live article', () =>
 test('creator studio build artifacts and contracts exist', () => {
 	assert.ok(exists('assets/creator-studio/package.json'));
 	assert.ok(exists('assets/creator-studio/package-lock.json'));
-	assert.ok(exists('assets/creator-studio/build/.gitkeep'));
 	// build/ is gitignored and deploy-only (same as assets/admin/build); when a
 	// local build is present, all three entry artifacts must be there together.
 	const built = ['index.asset.php', 'index.js', 'index.css'];
@@ -507,6 +506,30 @@ test('publish settings use a multi-select category picker and a creatable tag in
 	assert.match(appSource, /suggestions: \(bootstrap\.tags && bootstrap\.tags\.suggestions\)/);
 });
 
+// 二级 / 三级分类必须出现在投稿页：列表是完整层级树，白名单向下展开到子分类。
+test('submit categories resolve the full hierarchy and expand the whitelist', () => {
+	const categories = read('src/Core/SubmitCategories.php');
+	const submitContext = read('templates/parts/submit/context.php');
+	const save = read('src/Core/FrontSubmitSave.php');
+
+	// 不再用 parent=0 过滤，改为取全部分类后按父子关系展平。
+	assert.doesNotMatch(categories, /'parent'\s*=>\s*0/);
+	assert.match(categories, /get_term_children\(\$id, 'category'\)/);
+	assert.match(categories, /'number'\s*=>\s*0/);
+	assert.match(categories, /'depth'\s*=>\s*\$depth/);
+	// 父级不在集合里时，子分类仍作为根节点出现，不会被静默丢弃。
+	assert.match(categories, /if \(!isset\(\$present\[\$parent\]\)\) \{/);
+
+	// 创作者工作台与经典投稿表单共用同一份分类数据。
+	assert.match(creatorRest, /SubmitCategories::tree\(\$settings\)/);
+	assert.match(submitContext, /SubmitCategories::tree\(\$settings\)/);
+	assert.doesNotMatch(submitContext, /\$cat_args\['parent'\]\s*=\s*0/);
+
+	// 白名单与审核应用都走同一套"含后代"的过滤。
+	assert.match(save, /SubmitCategories::filter_ids\(\$categories, \$settings\)/);
+	assert.match(versions, /SubmitCategories::filter_ids\(\$cats, \$settings\)/);
+});
+
 test('scheduled publishing is validated and applied server side', () => {
 	const save = read('src/Core/FrontSubmitSave.php');
 	const rest = read('src/Core/CreatorRest.php');