fix: M-CHAT audit 修复 7 个缺陷

- A1/A2(P0): listSessions 响应格式 + ChatEntryContext Hashable
- A3: forceCreate 支持，新对话按钮创建新会话
- A4: loadSession 更新 entryContext (scope 标签)
- A6: 死代码清理 (itemIds + AIMessageCitation)
- A8: sessions sheet scope 过滤
- A10: deleteSession 错误处理

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

AIStudyApp/AIStudyApp/Core/Models/APIModels.swift

@@ -480,7 +480,7 @@ enum ChatScopeType: String, Codable {
     case global = "global"
 }
 
-struct ChatEntryContext {
+struct ChatEntryContext: Hashable {
     let scopeType: ChatScopeType
     let scopeId: String?
     let scopeName: String
@@ -541,6 +541,7 @@ struct CreateSessionRequest: Codable {
     let parentKnowledgeBaseId: String?
     let createdFrom: String
     let title: String?
+    let forceCreate: Bool?
 }
 
 struct UpdateChatSessionRequest: Codable {

AIStudyApp/AIStudyApp/Core/Services/APIService.swift

@@ -344,13 +344,14 @@ class RagChatService {
     static let shared = RagChatService()
     private let client = APIClient.shared
 
-    func createSession(ctx: ChatEntryContext) async throws -> ChatSession {
+    func createSession(ctx: ChatEntryContext, forceCreate: Bool = false) async throws -> ChatSession {
         let body = CreateSessionRequest(
             scopeType: ctx.scopeType.rawValue,
             scopeId: ctx.scopeId,
             parentKnowledgeBaseId: ctx.parentKnowledgeBaseId,
             createdFrom: ctx.createdFrom,
-            title: nil
+            title: nil,
+            forceCreate: forceCreate ? true : nil
         )
         return try await client.request("/rag-chat/sessions", method: "POST", body: body)
     }
@@ -360,7 +361,8 @@ class RagChatService {
         if let st = scopeType { items.append(URLQueryItem(name: "scopeType", value: st)) }
         if let si = scopeId { items.append(URLQueryItem(name: "scopeId", value: si)) }
         if let pk = parentKnowledgeBaseId { items.append(URLQueryItem(name: "parentKnowledgeBaseId", value: pk)) }
-        return try await client.request("/rag-chat/sessions", queryItems: items.isEmpty ? nil : items)
+        let page: PaginatedResponse<ChatSession> = try await client.request("/rag-chat/sessions", queryItems: items.isEmpty ? nil : items)
+        return page.data
     }
 
     func getMessages(sessionId: String) async throws -> [ChatMessage] {

AIStudyApp/AIStudyApp/Features/AI/AIChatPage.swift

@@ -114,8 +114,12 @@ struct AIChatPage: View {
                             .swipeActions(edge: .trailing, allowsFullSwipe: true) {
                                 Button(role: .destructive) {
                                     Task {
-                                        try? await RagChatService.shared.deleteSession(id: s.id)
+                                        do {
-                                        sessions.removeAll { $0.id == s.id }
+                                            try await RagChatService.shared.deleteSession(id: s.id)
+                                            sessions.removeAll { $0.id == s.id }
+                                        } catch {
+                                            // Keep session in list if delete failed
+                                        }
                                     }
                                 } label: { Label("删除", systemImage: "trash") }
                             }
@@ -128,7 +132,13 @@ struct AIChatPage: View {
             .frame(maxWidth: .infinity, maxHeight: .infinity).background(Color.zxBg0)
             .presentationDetents([.medium, .large])
             .task {
-                if let s = try? await RagChatService.shared.listSessions() { sessions = s }
+                let s: [ChatSession]
+                if let filter = vm.sessionListFilter {
+                    s = (try? await RagChatService.shared.listSessions(scopeType: filter.scopeType, scopeId: filter.scopeId)) ?? []
+                } else {
+                    s = (try? await RagChatService.shared.listSessions()) ?? []
+                }
+                sessions = s
             }
         }
         .task { await vm.load() }

AIStudyApp/AIStudyApp/Features/AI/AIChatViewModel.swift

@@ -19,12 +19,6 @@ struct AIMessage: Identifiable {
     }
 }
 
-struct AIMessageCitation: Identifiable {
-    let id: String
-    let title: String?
-    let content: String?
-}
-
 enum AIMessageRole {
     case user, ai
 }
@@ -39,7 +33,6 @@ final class AIChatViewModel: ObservableObject {
 
     private var sessionId: String?
     private var entryContext: ChatEntryContext?
-    private var itemIds: [String]?
 
     var canSend: Bool {
         !inputText.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty && !isSending && sessionId != nil
@@ -52,6 +45,11 @@ final class AIChatViewModel: ObservableObject {
         return "提问范围：\(ctx.scopeName)"
     }
 
+    var sessionListFilter: (scopeType: String, scopeId: String)? {
+        guard let ctx = entryContext, ctx.scopeType != .global, let sid = ctx.scopeId else { return nil }
+        return (ctx.scopeType.rawValue, sid)
+    }
+
     var scopeIcon: String {
         guard let ctx = entryContext else { return "globe" }
         switch ctx.scopeType {
@@ -101,7 +99,7 @@ final class AIChatViewModel: ObservableObject {
         )
 
         do {
-            let session = try await RagChatService.shared.createSession(ctx: ctx)
+            let session = try await RagChatService.shared.createSession(ctx: ctx, forceCreate: true)
             sessionId = session.id
             let scopeLabel = ctx.scopeType != .global ? "「\(ctx.scopeName)」的" : ""
             messages = [AIMessage(role: .ai, content: "你好！我是你的 AI 学习助手，基于\(scopeLabel)内容回答问题。")]
@@ -167,8 +165,27 @@ final class AIChatViewModel: ObservableObject {
         isCreatingSession = true
         do {
             let msgs: [ChatMessage] = try await RagChatService.shared.getMessages(sessionId: id)
+
+            // Update entryContext from the first message's scope snapshot (if available)
+            if let snapshot = msgs.first?.scopeSnapshot,
+               let scopeTypeStr = snapshot.scopeType,
+               let scopeType = ChatScopeType(rawValue: scopeTypeStr) {
+                entryContext = ChatEntryContext(
+                    scopeType: scopeType,
+                    scopeId: snapshot.scopeId,
+                    scopeName: scopeLabel ?? "AI 对话",
+                    parentKnowledgeBaseId: snapshot.parentKnowledgeBaseId,
+                    createdFrom: "session_switch"
+                )
+            }
+
+            let scopePrefix: String = {
+                guard let ctx = entryContext, ctx.scopeType != .global else { return "" }
+                return "「\(ctx.scopeName)」的"
+            }()
+
             if msgs.isEmpty {
-                messages = [AIMessage(role: .ai, content: "你好！我是你的 AI 学习助手，基于你的知识库回答问题。")]
+                messages = [AIMessage(role: .ai, content: "你好！我是你的 AI 学习助手，基于\(scopePrefix)内容回答问题。")]
             } else {
                 messages = msgs.map { m in
                     AIMessage(role: m.role == "user" ? .user : .ai, content: m.content, citations: m.citations)