feat: AIChat 全链路调试日志 + 错误详情展示

load/createSession/loadSession/send 都加了 print 日志:
- scope 参数
- 请求成功/失败状态
- 具体错误信息

sessionError 现在显示具体错误原因而非通用"创建对话失败"

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

AIStudyApp/AIStudyApp/Core/Services/APIService.swift

@@ -353,7 +353,15 @@ class RagChatService {
             title: nil,
             forceCreate: forceCreate ? true : nil
         )
-        return try await client.request("/rag-chat/sessions", method: "POST", body: body)
+        print("[RagChat] POST /rag-chat/sessions — scopeType=\(body.scopeType), scopeId=\(body.scopeId ?? "nil"), parentKB=\(body.parentKnowledgeBaseId ?? "nil"), forceCreate=\(forceCreate)")
+        do {
+            let session = try await client.request("/rag-chat/sessions", method: "POST", body: body) as ChatSession
+            print("[RagChat] createSession OK — id=\(session.id), scopeType=\(session.scopeType ?? "nil")")
+            return session
+        } catch {
+            print("[RagChat] createSession FAILED: \(error)")
+            throw error
+        }
     }
 
     func listSessions(scopeType: String? = nil, scopeId: String? = nil, parentKnowledgeBaseId: String? = nil) async throws -> [ChatSession] {

AIStudyApp/AIStudyApp/Features/AI/AIChatViewModel.swift

@@ -74,12 +74,18 @@ final class AIChatViewModel: ObservableObject {
             createdFrom: "global_ai_entry"
         )
 
+        print("[AIChat] load() entry — scopeType=\(ctx.scopeType.rawValue), scopeId=\(ctx.scopeId ?? "nil"), parentKB=\(ctx.parentKnowledgeBaseId ?? "nil")")
+
         do {
-            // open-or-create: backend handles find-or-create logic
             let session = try await RagChatService.shared.createSession(ctx: ctx)
+            print("[AIChat] open-or-create OK — sessionId=\(session.id), isNew=\(session.createdAt == session.updatedAt)")
             await loadSession(session.id)
         } catch {
-            sessionError = "创建对话失败"
+            print("[AIChat] open-or-create FAILED: \(error)")
+            if let apiErr = error as? APIError {
+                print("[AIChat] APIError detail: \(apiErr)")
+            }
+            sessionError = "创建对话失败: \(error.localizedDescription)"
             isCreatingSession = false
         }
     }
@@ -89,7 +95,6 @@ final class AIChatViewModel: ObservableObject {
         messages = []
         isCreatingSession = true
 
-        // Use entry context if available, otherwise default to global
         let ctx = entryContext ?? ChatEntryContext(
             scopeType: .global,
             scopeId: nil,
@@ -98,14 +103,18 @@ final class AIChatViewModel: ObservableObject {
             createdFrom: "global_ai_entry"
         )
 
+        print("[AIChat] createNewSession() — scopeType=\(ctx.scopeType.rawValue), scopeId=\(ctx.scopeId ?? "nil")")
+
         do {
             let session = try await RagChatService.shared.createSession(ctx: ctx, forceCreate: true)
+            print("[AIChat] forceCreate OK — sessionId=\(session.id)")
             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。")]
             isCreatingSession = false
         } catch {
-            sessionError = "创建对话失败"
+            print("[AIChat] forceCreate FAILED: \(error)")
+            sessionError = "创建对话失败: \(error.localizedDescription)"
             isCreatingSession = false
         }
     }
@@ -113,6 +122,7 @@ final class AIChatViewModel: ObservableObject {
     func send() {
         guard canSend, let sid = sessionId else { return }
         let text = inputText.trimmingCharacters(in: .whitespacesAndNewlines)
+        print("[AIChat] send — sessionId=\(sid), text=\(text.prefix(50))")
         messages.append(AIMessage(role: .user, content: text))
         inputText = ""
         isSending = true
@@ -139,10 +149,12 @@ final class AIChatViewModel: ObservableObject {
                             messages[idx] = AIMessage(role: .ai, content: reply, thinkingContent: thinking, isStreaming: true, id: placeholderId)
                         }
                     case "error":
+                        print("[AIChat] stream error: \(chunk.content ?? "unknown")")
                         if let idx = messages.firstIndex(where: { $0.id == placeholderId }) {
                             messages[idx] = AIMessage(role: .ai, content: "请求失败: \(chunk.content ?? "未知错误")")
                         }
                     case "done":
+                        print("[AIChat] stream done — reply=\(reply.count)chars, thinking=\(thinking.count)chars")
                         if let idx = messages.firstIndex(where: { $0.id == placeholderId }) {
                             messages[idx] = AIMessage(role: .ai, content: reply, thinkingContent: thinking.isEmpty ? nil : thinking)
                         }
@@ -150,6 +162,7 @@ final class AIChatViewModel: ObservableObject {
                     }
                 }
             } catch {
+                print("[AIChat] stream FAILED: \(error)")
                 if let idx = messages.firstIndex(where: { $0.id == placeholderId }) {
                     messages[idx] = AIMessage(role: .ai, content: "发送失败: \(error.localizedDescription)")
                 }
@@ -164,7 +177,9 @@ final class AIChatViewModel: ObservableObject {
         sessionId = id
         isCreatingSession = true
         do {
+            print("[AIChat] loadSession — id=\(id)")
             let msgs: [ChatMessage] = try await RagChatService.shared.getMessages(sessionId: id)
+            print("[AIChat] loadSession OK — \(msgs.count) messages")
 
             // Update entryContext from the first message's scope snapshot (if available)
             if let snapshot = msgs.first?.scopeSnapshot,
@@ -191,7 +206,10 @@ final class AIChatViewModel: ObservableObject {
                     AIMessage(role: m.role == "user" ? .user : .ai, content: m.content, citations: m.citations)
                 }
             }
-        } catch { sessionError = "加载对话失败" }
+        } catch {
+            print("[AIChat] loadSession FAILED: \(error)")
+            sessionError = "加载对话失败: \(error.localizedDescription)"
+        }
         isCreatingSession = false
     }
 }