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/launch.go

@@ -0,0 +1,250 @@
+package internal
+
+import (
+	"fmt"
+	"log"
+	"os/exec"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	"charm.land/bubbletea/v2"
+)
+
+// SessionAction 描述一个 Claude Code 会话启动动作
+type SessionAction struct {
+	Cwd       string // 工作目录
+	Title     string // 窗口标题
+	SessionID string // resume/fork 目标（空=新建）
+	Fork      bool   // 是否分叉
+	Prompt    string // 初始提示（fork 方向或 workspace prompt）
+	Name      string // --name 参数（workspace 启动用）
+}
+
+// Execute 执行启动动作
+func (a SessionAction) Execute(m *Model) {
+	if isWindows {
+		cwd := toWinPath(a.Cwd)
+		launchInWtWithTitle(cwd, a.Title, a.buildScript())
+	} else {
+		m.pendingCmd = a.buildScript()
+	}
+}
+
+// buildScript 根据平台构建启动脚本
+func (a SessionAction) buildScript() string {
+	if isWindows {
+		return a.pwshScript()
+	}
+	return a.bashScript()
+}
+
+func (a SessionAction) pwshScript() string {
+	var b strings.Builder
+	b.WriteString(fmt.Sprintf(`$Host.UI.RawUI.WindowTitle = "%s"`, a.Title))
+	b.WriteString(fmt.Sprintf("\n\t\tWrite-Host \"=== %s ===\" -ForegroundColor Cyan", a.Title))
+
+	if a.Prompt != "" && a.Name == "" {
+		// workspace prompt 显示
+		b.WriteString(fmt.Sprintf("\n\t\tWrite-Host \"Prompt: %s\" -ForegroundColor Yellow", a.Prompt))
+	}
+
+	b.WriteString(fmt.Sprintf("\n\t\tcd \"%s\"", toWinPath(a.Cwd)))
+	b.WriteString("\n\t\tclaude")
+
+	if a.SessionID != "" {
+		b.WriteString(fmt.Sprintf(" -r %s", a.SessionID))
+		if a.Fork {
+			b.WriteString(" --fork-session")
+		}
+	}
+	if a.Prompt != "" && a.SessionID != "" {
+		escaped := strings.ReplaceAll(a.Prompt, `"`, "`\"")
+		b.WriteString(fmt.Sprintf(` "%s"`, escaped))
+	}
+	if a.Name != "" {
+		b.WriteString(fmt.Sprintf(` --name "%s"`, a.Name))
+	}
+	b.WriteString(" --permission-mode bypassPermissions")
+	return b.String()
+}
+
+func (a SessionAction) bashScript() string {
+	var b strings.Builder
+	b.WriteString(fmt.Sprintf(`printf '\033]0;%s\007' && echo "=== %s ==="`, a.Title, a.Title))
+
+	if a.Prompt != "" && a.Name == "" {
+		b.WriteString(fmt.Sprintf(` && echo "Prompt: %s"`, a.Prompt))
+	}
+
+	b.WriteString(fmt.Sprintf(` && cd "%s"`, a.Cwd))
+	b.WriteString(" && claude")
+
+	if a.SessionID != "" {
+		b.WriteString(fmt.Sprintf(" -r %s", a.SessionID))
+		if a.Fork {
+			b.WriteString(" --fork-session")
+		}
+	}
+	if a.Prompt != "" && a.SessionID != "" {
+		escaped := strings.ReplaceAll(a.Prompt, "'", "'\\''")
+		b.WriteString(fmt.Sprintf(` '%s'`, escaped))
+	}
+	if a.Name != "" {
+		b.WriteString(fmt.Sprintf(` --name "%s"`, a.Name))
+	}
+	b.WriteString(" --permission-mode bypassPermissions")
+	return b.String()
+}
+
+// --- 启动辅助 ---
+
+func launchInWtWithTitle(dir, tabTitle, script string) {
+	encoded := encodePSCommand(script)
+	color := fmt.Sprintf("#%02X%02X%02X", randRange(80, 255), randRange(80, 255), randRange(80, 255))
+	args := []string{"-w", "0", "-d", dir, "--tabColor", color}
+	if tabTitle != "" {
+		args = append(args, "--title", tabTitle)
+	}
+	args = append(args, "pwsh", "-NoExit", "-EncodedCommand", encoded)
+	cmd := exec.Command("wt.exe", args...)
+	if err := cmd.Start(); err != nil {
+		log.Printf("[u-tabs] launch fail: %v", err)
+	}
+}
+
+// buildResumeAction 构建恢复会话动作
+func buildResumeAction(s *Session) SessionAction {
+	title := s.CustomTitle
+	if title == "" {
+		title = s.ID[:8]
+	}
+	return SessionAction{
+		Cwd:       s.Cwd,
+		Title:     "resume: " + title,
+		SessionID: s.ID,
+	}
+}
+
+// buildForkAction 构建分叉会话动作
+func buildForkAction(s *Session, prompt string) SessionAction {
+	title := s.CustomTitle
+	if title == "" {
+		title = s.ID[:8]
+	}
+	return SessionAction{
+		Cwd:       s.Cwd,
+		Title:     "fork: " + title,
+		SessionID: s.ID,
+		Fork:      true,
+		Prompt:    prompt,
+	}
+}
+
+// buildNewAction 构建新建会话动作
+func buildNewAction(cwd string) SessionAction {
+	title := filepath.Base(cwd) + " - new"
+	return SessionAction{
+		Cwd:   cwd,
+		Title: title,
+	}
+}
+
+// buildWorkspaceAction 构建工作空间启动动作
+func buildWorkspaceAction(ws Workspace) SessionAction {
+	return SessionAction{
+		Cwd:    ws.Dir,
+		Title:  ws.Title,
+		Prompt: ws.Prompt,
+		Name:   ws.Title,
+	}
+}
+
+// --- 会话操作 ---
+
+func (m *Model) resumeSelected() (*Model, tea.Cmd) {
+	s := m.currentSession()
+	if s == nil {
+		return m, nil
+	}
+	action := buildResumeAction(s)
+	action.Execute(m)
+	m.launched = "resume: " + s.CustomTitle
+	return m, nil
+}
+
+func (m *Model) newSessionFromHistory() (*Model, tea.Cmd) {
+	s := m.currentSession()
+	cwd := ""
+	if s != nil {
+		cwd = s.Cwd
+	} else {
+		cwd = m.currentDirCwd()
+	}
+	if cwd == "" {
+		return m, nil
+	}
+	action := buildNewAction(cwd)
+	action.Execute(m)
+	m.launched = "new: " + filepath.Base(cwd)
+	return m, nil
+}
+
+func (m *Model) executeFork() (*Model, tea.Cmd) {
+	s := m.currentSession()
+	if s == nil {
+		m.forkMode = false
+		return m, nil
+	}
+	m.forkMode = false
+
+	action := buildForkAction(s, m.forkBuf)
+	m.forkBuf = ""
+	action.Execute(m)
+
+	title := s.CustomTitle
+	if title == "" {
+		title = s.ID[:8]
+	}
+	m.launched = "fork: " + title
+	return m, nil
+}
+
+func (m *Model) launchSelected() (*Model, tea.Cmd) {
+	if len(m.selected) > 0 {
+		var launched []string
+		for idx := range m.selected {
+			ws := &AllWorkspaces[idx]
+			action := buildWorkspaceAction(*ws)
+			action.Execute(m)
+			launched = append(launched, ws.Title)
+		}
+		m.launched = strings.Join(launched, ", ")
+		m.selected = make(map[int]bool)
+		return m, nil
+	}
+	svcs := WorkspacesByGroup(Groups[m.activeGroup].Label)
+	if m.cursor < len(svcs) {
+		ws := svcs[m.cursor]
+		action := buildWorkspaceAction(ws)
+		action.Execute(m)
+		m.launched = ws.Title
+	}
+	return m, nil
+}
+
+func (m *Model) launchByInput() (*Model, tea.Cmd) {
+	num, err := strconv.Atoi(m.inputBuf)
+	if err != nil {
+		m.inputBuf = ""
+		return m, nil
+	}
+	ws := FindByNumber(num)
+	if ws != nil {
+		action := buildWorkspaceAction(*ws)
+		action.Execute(m)
+		m.launched = ws.Title
+	}
+	m.inputBuf = ""
+	return m, nil
+}