fix(ios): 拆分删除知识库和选择知识点按钮，避免误触

- 删除知识库 🗑 移到左侧灰色按钮，远离右侧操作区
- 选择知识点 ☑ 独立显示在右侧
- 不再共用 ⋯ 菜单

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

AIStudyApp/AIStudyApp/Features/Library/LibrarySubpages.swift

@@ -109,21 +109,19 @@ struct LibraryDetailPage: View {
                     .disabled(selectedIds.isEmpty)
                 }
             } else {
+                ToolbarItem(placement: .topBarLeading) {
+                    Button { showDeleteConfirm = true } label: {
+                        Image(systemName: "trash").font(.system(size: 16)).foregroundColor(Color.zxF03)
+                    }
+                }
                 ToolbarItem(placement: .topBarTrailing) {
                     NavigationLink(value: Route.addKnowledge(knowledgeBaseId: knowledgeBaseId)) {
                         Image(systemName: "plus").font(.system(size: 16, weight: .semibold)).foregroundColor(Color.zxPrimary)
                     }
                 }
                 ToolbarItem(placement: .topBarTrailing) {
-                    Menu {
+                    Button { isSelectMode = true } label: {
-                        Button { isSelectMode = true } label: {
+                        Image(systemName: "checkmark.circle").font(.system(size: 16)).foregroundColor(Color.zxF05)
-                            Label("选择知识点", systemImage: "checkmark.circle")
-                        }
-                        Button(role: .destructive) { showDeleteConfirm = true } label: {
-                            Label("删除知识库", systemImage: "trash")
-                        }
-                    } label: {
-                        Image(systemName: "ellipsis.circle").font(.system(size: 16)).foregroundColor(Color.zxF05)
                     }
                 }
             }