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>

main.go

@@ -1,5 +1,98 @@
 package main
 
+import (
+	"flag"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
 func main() {
-	// Placeholder - will be implemented in Task 2
+	noColor := flag.Bool("no-color", false, "Disable colored output")
+	flag.Parse()
+
+	if os.Getenv("NO_COLOR") != "" {
+		*noColor = true
+	}
+
+	args := flag.Args()
+	// Also check for --no-color after subcommand (flag stops at first non-flag)
+	var filteredArgs []string
+	for _, arg := range args {
+		if arg == "--no-color" {
+			*noColor = true
+		} else {
+			filteredArgs = append(filteredArgs, arg)
+		}
+	}
+
+	if len(filteredArgs) == 0 || filteredArgs[0] != "list" {
+		fmt.Fprintf(os.Stderr, "Usage: vmux list [--no-color]\n")
+		os.Exit(1)
+	}
+
+	processes, err := FindClaudeProcesses("/proc")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error scanning processes: %v\n", err)
+		os.Exit(1)
+	}
+
+	claudeDir := filepath.Join(os.Getenv("HOME"), ".claude", "projects")
+	now := time.Now()
+	var sessions []Session
+
+	for _, proc := range processes {
+		jsonlPath, messages, err := FindSessionForProcess(claudeDir, proc)
+		if err != nil {
+			sessions = append(sessions, Session{
+				Process: proc,
+				State:   Unknown,
+				CwdPath: proc.Cwd,
+			})
+			continue
+		}
+
+		state := DetectState(messages, now)
+		preview := ExtractPreview(messages)
+
+		var sessionID, gitBranch string
+		for _, msg := range messages {
+			if msg.SessionID != "" {
+				sessionID = msg.SessionID
+			}
+			if msg.GitBranch != "" {
+				gitBranch = msg.GitBranch
+			}
+		}
+
+		worktree := resolveWorktree(proc.Cwd)
+
+		_ = jsonlPath
+
+		sessions = append(sessions, Session{
+			Process:   proc,
+			SessionID: sessionID,
+			GitBranch: gitBranch,
+			State:     state,
+			Preview:   preview,
+			CwdPath:   proc.Cwd,
+			Worktree:  worktree,
+		})
+	}
+
+	DisplaySessions(os.Stdout, sessions, *noColor)
+}
+
+// resolveWorktree uses git to find the worktree root.
+// Falls back to cwd if git fails (not a git repo).
+func resolveWorktree(cwd string) string {
+	cmd := exec.Command("git", "-C", cwd, "rev-parse", "--show-toplevel")
+	out, err := cmd.Output()
+	if err != nil {
+		return cwd
+	}
+	return strings.TrimSpace(string(out))
 }