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_test.go

@@ -0,0 +1,115 @@
+package main
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestDisplaySessions_WithSessions(t *testing.T) {
+	sessions := []Session{
+		{
+			Process:   Process{PID: 100, Cwd: "/home/user/project-a"},
+			State:     Working,
+			CwdPath:   "/home/user/project-a",
+			GitBranch: "feat-login",
+			Preview:   "Implementing auth...",
+		},
+		{
+			Process:   Process{PID: 200, Cwd: "/home/user/project-b"},
+			State:     NeedsInput,
+			CwdPath:   "/home/user/project-b",
+			GitBranch: "main",
+			Preview:   "What should I do next?",
+		},
+	}
+
+	var buf bytes.Buffer
+	DisplaySessions(&buf, sessions, false)
+	output := buf.String()
+
+	for _, want := range []string{
+		"/home/user/project-a",
+		"feat-login",
+		"Working",
+		"Implementing auth...",
+		"/home/user/project-b",
+		"main",
+		"Needs Input",
+		"What should I do next?",
+	} {
+		if !strings.Contains(output, want) {
+			t.Errorf("output missing %q", want)
+		}
+	}
+}
+
+func TestDisplaySessions_NoColor(t *testing.T) {
+	sessions := []Session{
+		{
+			Process:   Process{PID: 100, Cwd: "/tmp"},
+			State:     Working,
+			CwdPath:   "/tmp",
+			GitBranch: "main",
+		},
+	}
+
+	var buf bytes.Buffer
+	DisplaySessions(&buf, sessions, true)
+	output := buf.String()
+
+	if strings.Contains(output, "\033") {
+		t.Errorf("noColor=true but output contains ANSI escape: %q", output)
+	}
+	if !strings.Contains(output, "Working") {
+		t.Error("output missing state label")
+	}
+}
+
+func TestDisplaySessions_Empty(t *testing.T) {
+	var buf bytes.Buffer
+	DisplaySessions(&buf, nil, false)
+	output := buf.String()
+
+	want := "No active Claude Code sessions found.\n"
+	if output != want {
+		t.Errorf("output = %q, want %q", output, want)
+	}
+}
+
+func TestDisplaySessions_WorktreeDiffers(t *testing.T) {
+	sessions := []Session{
+		{
+			Process:  Process{PID: 100, Cwd: "/home/user/repo/src"},
+			State:    Working,
+			CwdPath:  "/home/user/repo/src",
+			Worktree: "/home/user/repo",
+		},
+	}
+
+	var buf bytes.Buffer
+	DisplaySessions(&buf, sessions, true)
+	output := buf.String()
+
+	if !strings.Contains(output, "[worktree: /home/user/repo]") {
+		t.Errorf("output should show worktree when different from cwd: %q", output)
+	}
+}
+
+func TestDisplaySessions_NoBranch(t *testing.T) {
+	sessions := []Session{
+		{
+			Process: Process{PID: 100, Cwd: "/tmp"},
+			State:   Unknown,
+			CwdPath: "/tmp",
+		},
+	}
+
+	var buf bytes.Buffer
+	DisplaySessions(&buf, sessions, true)
+	output := buf.String()
+
+	if strings.Contains(output, "(") {
+		t.Errorf("no branch should mean no parentheses: %q", output)
+	}
+}