feat(timeline): TimelineRow + DateSection + grouping tests + Diary sheet

- TimelineRow: 时间线条目单行视图
- DateSection + TimelineGrouping: 今日/昨日/本周/更早分组
- DiaryQuickSheet: 文字日记快速记录入口
- TimelineGroupingTests: 分组逻辑烟测
- SymptomEndSheet / RootView: 配套微调

康康/Features/Timeline/TimelineRow.swift

@@ -0,0 +1,73 @@
+import SwiftUI
+
+struct TimelineRow: View {
+    let entry: TimelineEntry
+
+    var body: some View {
+        HStack(spacing: 12) {
+            ZStack {
+                RoundedRectangle(cornerRadius: 8, style: .continuous)
+                    .fill(entry.kind.accent.opacity(0.12))
+                Image(systemName: entry.kind.icon)
+                    .font(.system(size: 14, weight: .semibold))
+                    .foregroundStyle(entry.kind.accent)
+            }
+            .frame(width: 36, height: 36)
+            .overlay(alignment: .topTrailing) {
+                if entry.isOngoing {
+                    Circle()
+                        .fill(Tj.Palette.brick)
+                        .frame(width: 7, height: 7)
+                        .overlay(Circle().strokeBorder(Tj.Palette.sand, lineWidth: 1.5))
+                        .offset(x: 3, y: -3)
+                }
+            }
+
+            VStack(alignment: .leading, spacing: 2) {
+                Text("\(entry.date.timelineLabel) · \(entry.subtitle)")
+                    .font(.system(size: 11))
+                    .tracking(0.3)
+                    .foregroundStyle(Tj.Palette.text3)
+                    .lineLimit(1)
+                Text(entry.title)
+                    .font(.system(size: 14, weight: .medium))
+                    .foregroundStyle(Tj.Palette.text)
+                    .lineLimit(1)
+                    .truncationMode(.tail)
+            }
+            Spacer(minLength: 8)
+            if let trailing = entry.trailing {
+                Text(trailing)
+                    .font(.system(size: 12, weight: .semibold, design: .monospaced))
+                    .foregroundStyle(entry.trailingIsAlert ? Tj.Palette.brick : Tj.Palette.text2)
+                    .lineLimit(1)
+                    .fixedSize()
+            }
+        }
+        .padding(12)
+        .tjCard(bordered: true)
+    }
+}
+
+extension Date {
+    var timelineLabel: String {
+        let cal = Calendar.current
+        if cal.isDateInToday(self) {
+            return self.formatted(date: .omitted, time: .shortened)
+        }
+        if cal.isDateInYesterday(self) {
+            return "昨天 " + self.formatted(date: .omitted, time: .shortened)
+        }
+        let now = Date.now
+        if cal.isDate(self, equalTo: now, toGranularity: .year) {
+            let f = DateFormatter()
+            f.locale = Locale(identifier: "zh_CN")
+            f.dateFormat = "M 月 d 日"
+            return f.string(from: self)
+        }
+        let f = DateFormatter()
+        f.locale = Locale(identifier: "zh_CN")
+        f.dateFormat = "yyyy 年 M 月 d 日"
+        return f.string(from: self)
+    }
+}