根据提供的code differences信息，由于没有具体的代码变更内容，我将生成一个通用的commit message模板：

```
docs(readme): 更新文档说明

- 添加了项目使用指南
- 完善了API接口说明
- 修正了一些文字错误
```

注：由于未提供具体的代码差异信息，以上为示例格式。请提供具体的代码变更内容以便生成准确的commit message。

康康/Features/Archive/HealthExportSheet.swift

@@ -19,6 +19,7 @@ struct HealthExportSheet: View {
     @State private var error: Error?
     @State private var completed: Bool = false
     @State private var copiedFlash: Bool = false
+    @State private var lastScrollAt: Date = .distantPast   // 流式滚动节流时间戳
     @State private var answeringTurnID: UUID?
     @State private var retrieval: HealthExportService.RetrievalSummary?
     @State private var turnRetrievals: [UUID: HealthExportService.RetrievalSummary] = [:]
@@ -57,7 +58,7 @@ struct HealthExportSheet: View {
             header
             ScrollViewReader { proxy in
                 ScrollView {
-                    VStack(alignment: .leading, spacing: 18) {
+                    LazyVStack(alignment: .leading, spacing: 18) {
                         introSection
 
                         ForEach(turns) { turn in
@@ -76,15 +77,15 @@ struct HealthExportSheet: View {
                     .padding(.horizontal, 20)
                     .padding(.vertical, 16)
                 }
-                .onChange(of: content) { _, _ in
-                    withAnimation(.easeOut(duration: 0.12)) {
-                        proxy.scrollTo("bottom", anchor: .bottom)
-                    }
+                // 流式期间 content / turns 每 token 都变,逐次动画滚动会造成布局抖动;
+                // 节流到 ~8Hz,并在生成完成时补一次滚动确保停在底部。
+                .onChange(of: content) { _, _ in throttledScrollToBottom(proxy) }
+                .onChange(of: turns) { _, _ in throttledScrollToBottom(proxy) }
+                .onChange(of: completed) { _, done in
+                    if done { scrollToBottom(proxy) }
                 }
-                .onChange(of: turns) { _, _ in
-                    withAnimation(.easeOut(duration: 0.12)) {
-                        proxy.scrollTo("bottom", anchor: .bottom)
-                    }
+                .onChange(of: answeringTurnID) { _, id in
+                    if id == nil { scrollToBottom(proxy) }
                 }
             }
             if completed {
@@ -358,7 +359,7 @@ struct HealthExportSheet: View {
             HStack(spacing: 8) {
                 Image(systemName: "exclamationmark.triangle.fill")
                     .foregroundStyle(Tj.Palette.brick)
-                Text(err.localizedDescription)
+                Text(friendlyMessage(for: err))
                     .font(.tjScaled( 13))
                     .foregroundStyle(Tj.Palette.text)
             }
@@ -504,8 +505,16 @@ struct HealthExportSheet: View {
                 questionFocused = true
             } catch {
                 answeringTurnID = nil
-                appendToTurn(id: assistantTurn.id, text: error.localizedDescription)
                 questionFocused = true
+                if error is CancellationError { return }
+                #if DEBUG
+                print("[HealthExport] answer failed: \(error)")
+                #endif
+                // 已有部分回答就保留;否则给一句友好兜底,绝不把技术异常当成 AI 的回答展示。
+                if let idx = turns.firstIndex(where: { $0.id == assistantTurn.id }),
+                   turns[idx].text.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
+                    turns[idx].text = "这次没能回答上来,请换个说法再试一次。"
+                }
             }
         }
     }
@@ -552,6 +561,10 @@ struct HealthExportSheet: View {
                     }
                 }
             } catch {
+                if error is CancellationError { return }
+                #if DEBUG
+                print("[HealthExport] export failed: \(error)")
+                #endif
                 self.error = error
                 self.phase = nil
             }
@@ -600,6 +613,27 @@ struct HealthExportSheet: View {
         task?.cancel()
         dismiss()
     }
+
+    // MARK: - 滚动
+
+    private func scrollToBottom(_ proxy: ScrollViewProxy) {
+        lastScrollAt = Date()
+        withAnimation(.easeOut(duration: 0.12)) {
+            proxy.scrollTo("bottom", anchor: .bottom)
+        }
+    }
+
+    /// 节流滚动:流式 token 高频触发,限制到约 8Hz,避免每 token 一次动画布局。
+    private func throttledScrollToBottom(_ proxy: ScrollViewProxy) {
+        guard Date().timeIntervalSince(lastScrollAt) > 0.12 else { return }
+        scrollToBottom(proxy)
+    }
+
+    /// 把推理过程中抛出的技术异常翻译成用户能看懂的一句话(取消不算错误)。
+    private func friendlyMessage(for error: Error) -> String {
+        if error is CancellationError { return "" }
+        return "这次没能生成成功,请稍后重试。"
+    }
 }
 
 // MARK: - 检索结果 chips(本地 RAG 可视化)
@@ -757,15 +791,30 @@ struct MarkdownView: View {
         return nil
     }
 
+    /// 行内样式缓存:流式生成时整段会被反复重渲染,缓存命中可避免对同一行重复跑昂贵的
+    /// markdown 解析。键为行文本,稳定的历史行命中缓存,只有正在增长的尾行才真正解析。
+    private final class AttrBox { let value: AttributedString; init(_ v: AttributedString) { value = v } }
+    private static let inlineCache: NSCache<NSString, AttrBox> = {
+        let c = NSCache<NSString, AttrBox>()
+        c.countLimit = 256
+        return c
+    }()
+
     private func inline(_ s: String) -> AttributedString {
+        // 快路径:整段报告里绝大多数行(标题、普通条目、纯正文)都没有内联标记,
+        // 直接走纯文本,跳过 AttributedString(markdown:) —— 这是流式期间最大的一笔开销。
+        if !s.contains(where: { $0 == "*" || $0 == "_" || $0 == "[" || $0 == "`" }) {
+            return AttributedString(s)
+        }
+        let key = s as NSString
+        if let hit = Self.inlineCache.object(forKey: key) { return hit.value }
         // **bold** / *italic* / [text](url) 走 AttributedString markdown 解析
-        if let attr = try? AttributedString(
+        let attr = (try? AttributedString(
             markdown: s,
             options: .init(interpretedSyntax: .inlineOnlyPreservingWhitespace)
-        ) {
-            return attr
-        }
-        return AttributedString(s)
+        )) ?? AttributedString(s)
+        Self.inlineCache.setObject(AttrBox(attr), forKey: key)
+        return attr
     }
 
     // MARK: - 行级解析