feat(ios): 知识库详情页 - toolbar 按钮 + 删除功能

- + 和删除按钮移入导航栏 toolbar，与系统返回按钮同行
- 新增删除确认弹窗（alert with destructive action）
- LibraryDetailViewModel 新增 deleteKnowledgeBase 方法
- 删除成功后 toast + 自动返回列表

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

AIStudyApp/AIStudyApp/Features/Library/LibrarySubpages.swift

@@ -39,15 +39,13 @@ struct CreateLibraryPage: View {
 
 struct LibraryDetailPage: View {
     let knowledgeBaseId: String
+    @Environment(\.dismiss) private var dismiss
     @StateObject private var viewModel = LibraryDetailViewModel()
+    @State private var showDeleteConfirm = false
+    @State private var isDeleting = false
+
     var body: some View {
         ZStack { Color.zxBg0.ignoresSafeArea(); VStack(spacing: 0) {
-            HStack { Spacer()
-                NavigationLink(value: Route.addKnowledge(knowledgeBaseId: knowledgeBaseId)) {
-                    Image(systemName: "plus").font(.system(size: 18)).foregroundColor(.white)
-                        .frame(width: 36, height: 36).background(ZXGradient.brand).clipShape(RoundedRectangle(cornerRadius: 10))
-                }
-            }.padding(.horizontal, 20).padding(.top, 8).padding(.bottom, 8)
             ScrollView { VStack(spacing: 12) {
                 if viewModel.isLoading && viewModel.items.isEmpty {
                     VStack(spacing: 12) { ZXLoadingView(size: 36, lineWidth: 3); Text("加载中…").font(.system(size: 13)).foregroundColor(Color.zxF04) }
@@ -67,7 +65,39 @@ struct LibraryDetailPage: View {
             }.padding(.horizontal, 20).padding(.bottom, 80) }
             .scrollIndicators(.hidden)
             .zxPullToRefresh { await viewModel.refresh(knowledgeBaseId: knowledgeBaseId) } }
-        }.navigationBarTitleDisplayMode(.inline).toolbarBackground(.hidden, for: .navigationBar)
+        }
+        .navigationBarTitleDisplayMode(.inline).toolbarBackground(.hidden, for: .navigationBar)
+        .toolbar {
+            ToolbarItem(placement: .topBarTrailing) {
+                NavigationLink(value: Route.addKnowledge(knowledgeBaseId: knowledgeBaseId)) {
+                    Image(systemName: "plus").font(.system(size: 16, weight: .semibold))
+                        .foregroundColor(Color.zxPrimary)
+                }
+            }
+            ToolbarItem(placement: .topBarTrailing) {
+                Button {
+                    showDeleteConfirm = true
+                } label: {
+                    Image(systemName: "trash").font(.system(size: 16))
+                        .foregroundColor(Color.zxCoral)
+                }
+            }
+        }
+        .alert("删除知识库", isPresented: $showDeleteConfirm) {
+            Button("取消", role: .cancel) {}
+            Button("删除", role: .destructive) {
+                isDeleting = true
+                Task {
+                    await viewModel.deleteKnowledgeBase(id: knowledgeBaseId)
+                    await MainActor.run {
+                        isDeleting = false
+                        dismiss()
+                    }
+                }
+            }
+        } message: {
+            Text("删除后将无法恢复，包括其中的所有知识点。确定要删除吗？")
+        }
         .task { await viewModel.loadItems(knowledgeBaseId: knowledgeBaseId) }
     }
 }

AIStudyApp/AIStudyApp/Features/Library/LibraryViewModel.swift

@@ -129,6 +129,15 @@ class LibraryDetailViewModel: ObservableObject {
         } catch {}
     }
 
+    func deleteKnowledgeBase(id: String) async {
+        do {
+            _ = try await KnowledgeBaseService.shared.delete(id: id)
+            ZXToastManager.shared.success("知识库已删除")
+        } catch {
+            ZXToastManager.shared.error("删除失败")
+        }
+    }
+
     func addItem(knowledgeBaseId: String, title: String, content: String?) async -> KnowledgeItem? {
         do {
             let item = try await KnowledgeItemService.shared.create(