新增: 会话分叉功能，优化增量扫描缓存

- 会话分叉: 按 c 键从历史会话分叉，支持带方向提示
- 启动自动加载历史记录
- 增量扫描: 缓存内存化、目录 modTime 跳过、已删除条目裁剪
- 刷新按钮复用 onTabSwitch 单一入口

internal/view.go

@@ -0,0 +1,155 @@
+package internal
+
+import (
+	"fmt"
+	"strings"
+
+	"charm.land/bubbletea/v2"
+	"charm.land/lipgloss/v2"
+	"u-tabs/internal/style"
+)
+
+// --- View 入口 ---
+
+func (m *Model) View() tea.View {
+	v := tea.NewView(m.render())
+	v.AltScreen = true
+	v.MouseMode = tea.MouseModeCellMotion
+	v.WindowTitle = "U-TABS"
+	return v
+}
+
+func (m *Model) render() string {
+	if m.width == 0 {
+		return "loading..."
+	}
+
+	var b strings.Builder
+
+	b.WriteString(m.renderTabBar())
+	b.WriteString("\n")
+	b.WriteString(lipgloss.NewStyle().Foreground(style.BgPanel).Render(strings.Repeat("─", m.width)))
+	b.WriteString("\n")
+
+	if m.IsHistoryTab() {
+		b.WriteString(m.renderHistory())
+	} else {
+		b.WriteString(m.renderWorkspace())
+	}
+
+	// footer
+	b.WriteString("\n")
+	if m.inputBuf != "" {
+		b.WriteString(style.InputStyle.Render(fmt.Sprintf(" ▶ num:%s [Enter]go [Esc]cancel", m.inputBuf)))
+	}
+	if m.forkMode {
+		b.WriteString(style.InputStyle.Render(fmt.Sprintf(" ⎇ fork:%s [Enter]confirm [Esc]cancel", m.forkBuf)))
+	}
+	if m.launched != "" {
+		b.WriteString(lipgloss.NewStyle().Foreground(style.Accent).Render(fmt.Sprintf(" ✓ %s", m.launched)))
+		m.launched = ""
+	}
+	if m.update.Done {
+		b.WriteString(lipgloss.NewStyle().Foreground(style.Success).Bold(true).
+			Render(fmt.Sprintf(" updated to v%s, restart to apply", m.update.NewVersion)))
+	} else if m.update.Error != nil {
+		b.WriteString(lipgloss.NewStyle().Foreground(style.Red).
+			Render(fmt.Sprintf(" update failed: %v", m.update.Error)))
+	} else if m.update.Updating {
+		b.WriteString(lipgloss.NewStyle().Foreground(style.Warning).
+			Render(" updating..."))
+	} else if m.update.Available {
+		b.WriteString(lipgloss.NewStyle().Foreground(style.Warning).Bold(true).
+			Render(fmt.Sprintf(" v%s available [u]update", m.update.NewVersion)))
+	}
+	b.WriteString("\n")
+
+	helpParts := m.renderHelp()
+	helpStr := " " + strings.Join(helpParts, "  ")
+	verStr := lipgloss.NewStyle().Foreground(style.Dim).Render("绝尘 v" + Version)
+	padW := m.width - lipgloss.Width(helpStr) - lipgloss.Width(verStr)
+	if padW > 0 {
+		b.WriteString(helpStr + strings.Repeat(" ", padW) + verStr)
+	} else {
+		b.WriteString(helpStr + "  " + verStr)
+	}
+
+	if hint := ConfigHint(); hint != "" {
+		b.WriteString("\n" + hint)
+	}
+	return b.String()
+}
+
+// renderTabBar 顶部两个主 tab
+func (m *Model) renderTabBar() string {
+	var b strings.Builder
+	b.WriteString(style.TitleStyle.Render(" U-TABS "))
+	sep := style.TabSep.Render(" │ ")
+
+	wsLabel := " 1 工作空间 "
+	if !m.IsHistoryTab() {
+		b.WriteString(lipgloss.NewStyle().
+			Bold(true).Background(style.BgPanel).Foreground(style.Accent).
+			Render(wsLabel))
+	} else {
+		b.WriteString(style.TabInactiveStyle.Render(wsLabel))
+	}
+
+	b.WriteString(sep)
+	histLabel := " 2 历史对话 "
+	if m.IsHistoryTab() {
+		b.WriteString(lipgloss.NewStyle().
+			Bold(true).Background(style.BgPanel).Foreground(style.Cyan).
+			Render(histLabel))
+	} else {
+		b.WriteString(style.TabInactiveStyle.Render(histLabel))
+	}
+
+	return b.String()
+}
+
+func (m *Model) renderHelp() []string {
+	if m.IsHistoryTab() {
+		return []string{
+			m.fmtHelp("↑↓", "sel"),
+			m.fmtHelp("←→", "panel"),
+			m.fmtHelp("Enter", "resume"),
+			m.fmtHelp("f", "star"),
+			m.fmtHelp("n", "new"),
+			m.fmtHelp("c", "fork"),
+			m.fmtHelp("1", "workspace"),
+			m.fmtHelp("r/F5", "refresh"),
+			m.fmtHelp("q", "quit"),
+		}
+	}
+	return []string{
+		m.fmtHelp("←→", "col"),
+		m.fmtHelp("↑↓", "sel"),
+		m.fmtHelp("Enter", "run"),
+		m.fmtHelp("2", "history"),
+		m.fmtHelp("q", "quit"),
+	}
+}
+
+func (m *Model) fmtHelp(key, desc string) string {
+	return lipgloss.NewStyle().Foreground(style.Accent).Render(key) +
+		lipgloss.NewStyle().Foreground(style.Dim).Render(":" + desc)
+}
+
+func renderNavEntry(lines *[]string, w int, label string, activeFg string, isCur, focused bool) {
+	sep := lipgloss.NewStyle().Foreground(style.BgPanel).Render(fitWidth(" ─────────", w))
+	*lines = append(*lines, sep)
+	if isCur {
+		curLabel := " → " + label
+		line := padRightByWidth(truncateByWidth(curLabel, w), w)
+		if focused {
+			*lines = append(*lines, style.SelStyle.Render(line))
+		} else {
+			*lines = append(*lines, lipgloss.NewStyle().Foreground(lipgloss.Color(activeFg)).Bold(true).Render(line))
+		}
+	} else {
+		inactiveLabel := "   " + label
+		line := padRightByWidth(truncateByWidth(inactiveLabel, w), w)
+		*lines = append(*lines, lipgloss.NewStyle().Foreground(style.Dim).Render(line))
+	}
+}