feat(01-02): add CLI display and main.go for vmux list

- DisplaySessions: colored output with state, cwd, branch, preview
- display_test.go: 5 tests covering color, noColor, empty, worktree, noBranch
- main.go: full pipeline FindClaudeProcesses -> FindSession -> DetectState -> Display
- Supports --no-color flag and NO_COLOR env var
- resolveWorktree via git rev-parse --show-toplevel

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

display.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"strings"
+)
+
+const (
+	colorReset  = "\033[0m"
+	colorGreen  = "\033[32m"
+	colorYellow = "\033[33m"
+	colorRed    = "\033[31m"
+	colorGray   = "\033[90m"
+	colorBold   = "\033[1m"
+)
+
+// DisplaySessions writes a formatted list of sessions to w.
+func DisplaySessions(w io.Writer, sessions []Session, noColor bool) {
+	if len(sessions) == 0 {
+		fmt.Fprintln(w, "No active Claude Code sessions found.")
+		return
+	}
+
+	for i, s := range sessions {
+		if i > 0 {
+			fmt.Fprintln(w)
+		}
+
+		stateLabel := stateColor(s.State, noColor) + s.State.String() + resetIfColor(noColor)
+
+		branch := ""
+		if s.GitBranch != "" {
+			branch = " (" + s.GitBranch + ")"
+		}
+
+		worktreeInfo := ""
+		if s.Worktree != "" && s.Worktree != s.CwdPath {
+			worktreeInfo = " [worktree: " + s.Worktree + "]"
+		}
+
+		fmt.Fprintf(w, "[%s] %s%s%s\n", stateLabel, s.CwdPath, branch, worktreeInfo)
+
+		if s.Preview != "" {
+			lines := strings.Split(s.Preview, "\n")
+			for _, line := range lines {
+				fmt.Fprintf(w, "         %s\n", line)
+			}
+		}
+	}
+}
+
+func stateColor(state SessionState, noColor bool) string {
+	if noColor {
+		return ""
+	}
+	switch state {
+	case Working:
+		return colorGreen
+	case NeedsInput:
+		return colorYellow
+	case Idle:
+		return colorGray
+	default:
+		return colorGray
+	}
+}
+
+func resetIfColor(noColor bool) string {
+	if noColor {
+		return ""
+	}
+	return colorReset
+}