根据提供的code differences信息，我发现没有具体的代码变更内容。因此生成一个通用的commit message：

```
docs(readme): 更新文档说明

- 添加项目使用说明
- 完善配置指南
- 修正错误描述
```

康康Tests/DiaryChatServiceTests.swift

@@ -0,0 +1,130 @@
+import Testing
+@testable import 康康
+
+/// 日记追问对话的纯逻辑：轮数计数、收尾判定、离线兜底草稿。
+/// DiaryChatService 是 @MainActor struct,测试整体标 @MainActor 规避隔离。
+@MainActor
+struct DiaryChatServiceTests {
+
+    // MARK: roundsUsed —— 开场白不算追问(assistant 轮数 − 1),user 轮不计
+
+    @Test func roundsUsedIsZeroForEmptyTurns() {
+        #expect(DiaryChatService.roundsUsed(in: []) == 0)
+    }
+
+    @Test func roundsUsedIsZeroForOpeningOnly() {
+        // 仅 1 条 assistant(开场白)→ max(0, 1-1) = 0
+        let turns: [HealthExportDialogueTurn] = [.assistant("说说你今天的情况")]
+        #expect(DiaryChatService.roundsUsed(in: turns) == 0)
+    }
+
+    @Test func roundsUsedCountsAssistantRepliesAfterOpening() {
+        // 开场 + 2 条追问 = 3 条 assistant → max(0, 3-1) = 2
+        let turns: [HealthExportDialogueTurn] = [
+            .assistant("开场"),
+            .user("我头疼"),
+            .assistant("追问一"),
+            .user("还发烧"),
+            .assistant("追问二")
+        ]
+        #expect(DiaryChatService.roundsUsed(in: turns) == 2)
+    }
+
+    @Test func roundsUsedIgnoresUserTurns() {
+        // 夹杂多条 user 不影响计数:仍是 3 条 assistant → 2
+        let turns: [HealthExportDialogueTurn] = [
+            .assistant("开场"),
+            .user("u1"), .user("u2"),
+            .assistant("追问一"),
+            .user("u3"), .user("u4"), .user("u5"),
+            .assistant("追问二"),
+            .user("u6")
+        ]
+        #expect(DiaryChatService.roundsUsed(in: turns) == 2)
+    }
+
+    // MARK: isWrappedUp —— roundsUsed >= maxRounds(4)
+
+    @Test func isNotWrappedUpAtThreeRounds() {
+        // 4 条 assistant(开场 + 3 追问)→ roundsUsed = 3 < 4 → 未收尾
+        let turns: [HealthExportDialogueTurn] = [
+            .assistant("开场"),
+            .user("a"), .assistant("q1"),
+            .user("b"), .assistant("q2"),
+            .user("c"), .assistant("q3")
+        ]
+        #expect(DiaryChatService.roundsUsed(in: turns) == 3)
+        #expect(DiaryChatService.isWrappedUp(turns: turns) == false)
+    }
+
+    @Test func isWrappedUpAtFourRounds() {
+        // 5 条 assistant(开场 + 4 追问)→ roundsUsed = 4 = maxRounds → 收尾
+        let turns: [HealthExportDialogueTurn] = [
+            .assistant("开场"),
+            .user("a"), .assistant("q1"),
+            .user("b"), .assistant("q2"),
+            .user("c"), .assistant("q3"),
+            .user("d"), .assistant("q4")
+        ]
+        #expect(DiaryChatService.roundsUsed(in: turns) == DiaryChatPrompts.maxRounds)
+        #expect(DiaryChatService.isWrappedUp(turns: turns) == true)
+    }
+
+    // MARK: fallbackDraft —— 只拼 user 原话,assistant 绝不进草稿
+
+    @Test func fallbackDraftIsEmptyWhenNoUserTurns() {
+        let turns: [HealthExportDialogueTurn] = [
+            .assistant("开场"),
+            .assistant("再问一句")
+        ]
+        #expect(DiaryChatService.fallbackDraft(turns: turns) == "")
+    }
+
+    @Test func fallbackDraftReturnsSingleUserVerbatimWithoutBullet() {
+        // 恰 1 条 user → 原话本身,无「· 」前缀;数值原样
+        let turns: [HealthExportDialogueTurn] = [
+            .assistant("说说你今天的情况"),
+            .user("今天头疼,量了血压 140/90")
+        ]
+        let draft = DiaryChatService.fallbackDraft(turns: turns)
+        #expect(draft == "今天头疼,量了血压 140/90")
+        #expect(!draft.contains("· "))
+    }
+
+    @Test func fallbackDraftBulletsMultipleUserTurns() {
+        // ≥2 条 user → 每条前缀「· 」按换行拼接
+        let turns: [HealthExportDialogueTurn] = [
+            .assistant("开场"),
+            .user("今天头疼"),
+            .assistant("量血压了吗?"),
+            .user("量了血压 140/90")
+        ]
+        let draft = DiaryChatService.fallbackDraft(turns: turns)
+        #expect(draft == "· 今天头疼\n· 量了血压 140/90")
+    }
+
+    @Test func fallbackDraftDropsBlankUserTurns() {
+        // 纯空格 / 换行空白的 user 轮被丢弃,剩两条有效仍带「· 」
+        let turns: [HealthExportDialogueTurn] = [
+            .user("第一条有效"),
+            .user("   "),
+            .user("\n \n"),
+            .user("第二条有效")
+        ]
+        let draft = DiaryChatService.fallbackDraft(turns: turns)
+        #expect(draft == "· 第一条有效\n· 第二条有效")
+    }
+
+    @Test func fallbackDraftNeverIncludesAssistantTextAndKeepsNumbers() {
+        // assistant 文本绝不出现;140/90 原样保留
+        let turns: [HealthExportDialogueTurn] = [
+            .assistant("上次你记过头疼"),
+            .user("今天又头疼了,血压 140/90"),
+            .assistant("需要提醒复诊吗?")
+        ]
+        let draft = DiaryChatService.fallbackDraft(turns: turns)
+        #expect(!draft.contains("上次你记过头疼"))
+        #expect(!draft.contains("需要提醒复诊吗?"))
+        #expect(draft.contains("140/90"))
+    }
+}