Fix bd-73: Add git worktree detection and warnings

- Implement robust worktree detection using git-dir vs git-common-dir comparison
- Add prominent warning when daemon mode is active in a worktree
- Warn in 3 places: initial connection, auto-start, and daemon start command
- Show shared database path and clarify BEADS_AUTO_START_DAEMON behavior
- Document limitations and solutions in README.md and AGENTS.md
- Add comprehensive tests for detection and path truncation

Fixes #55

Amp-Thread-ID: https://ampcode.com/threads/T-254eb9e3-1a42-42d7-afdf-b7ca2d2dcb8b
Co-authored-by: Amp <amp@ampcode.com>

cmd/bd/worktree_test.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+)
+
+func TestIsGitWorktree(t *testing.T) {
+	// Save current directory
+	origDir, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Chdir(origDir)
+
+	// Create a temp directory for our test repo
+	tmpDir := t.TempDir()
+	
+	// Initialize a git repo
+	mainRepo := filepath.Join(tmpDir, "main")
+	if err := os.Mkdir(mainRepo, 0755); err != nil {
+		t.Fatal(err)
+	}
+	
+	// Initialize main git repo
+	if err := os.Chdir(mainRepo); err != nil {
+		t.Fatal(err)
+	}
+	
+	if err := exec.Command("git", "init").Run(); err != nil {
+		t.Skip("git not available")
+	}
+	
+	if err := exec.Command("git", "config", "user.email", "test@example.com").Run(); err != nil {
+		t.Fatal(err)
+	}
+	if err := exec.Command("git", "config", "user.name", "Test User").Run(); err != nil {
+		t.Fatal(err)
+	}
+	
+	// Create a commit
+	readmeFile := filepath.Join(mainRepo, "README.md")
+	if err := os.WriteFile(readmeFile, []byte("# Test\n"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	if err := exec.Command("git", "add", "README.md").Run(); err != nil {
+		t.Fatal(err)
+	}
+	if err := exec.Command("git", "commit", "-m", "Initial commit").Run(); err != nil {
+		t.Fatal(err)
+	}
+	
+	// Test 1: Main repo should NOT be a worktree
+	if isGitWorktree() {
+		t.Error("Main repository should not be detected as a worktree")
+	}
+	
+	// Create a worktree
+	worktreeDir := filepath.Join(tmpDir, "worktree")
+	if err := exec.Command("git", "worktree", "add", worktreeDir, "-b", "feature").Run(); err != nil {
+		t.Skip("git worktree not available")
+	}
+	
+	// Change to worktree directory
+	if err := os.Chdir(worktreeDir); err != nil {
+		t.Fatal(err)
+	}
+	
+	// Test 2: Worktree should be detected
+	if !isGitWorktree() {
+		t.Error("Worktree should be detected as a worktree")
+	}
+	
+	// Test 3: Verify git-dir != git-common-dir in worktree
+	wtGitDir := gitRevParse("--git-dir")
+	wtCommonDir := gitRevParse("--git-common-dir")
+	if wtGitDir == "" || wtCommonDir == "" {
+		t.Error("git rev-parse should return valid paths in worktree")
+	}
+	if wtGitDir == wtCommonDir {
+		t.Errorf("In worktree, git-dir (%s) should differ from git-common-dir (%s)", wtGitDir, wtCommonDir)
+	}
+	
+	// Clean up worktree
+	if err := os.Chdir(mainRepo); err != nil {
+		t.Fatal(err)
+	}
+	if err := exec.Command("git", "worktree", "remove", worktreeDir).Run(); err != nil {
+		t.Logf("Warning: failed to clean up worktree: %v", err)
+	}
+}
+
+func TestTruncateForBox(t *testing.T) {
+	tests := []struct {
+		name   string
+		path   string
+		maxLen int
+		want   string
+	}{
+		{"short path", "/home/user", 20, "/home/user"},
+		{"exact length", "/home/user/test", 15, "/home/user/test"},
+		{"long path", "/very/long/path/to/database/file.db", 20, ".../database/file.db"},
+	}
+	
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := truncateForBox(tt.path, tt.maxLen)
+			if len(got) > tt.maxLen {
+				t.Errorf("truncateForBox() result too long: got %d chars, want <= %d", len(got), tt.maxLen)
+			}
+			if len(tt.path) <= tt.maxLen && got != tt.path {
+				t.Errorf("truncateForBox() shouldn't truncate short paths: got %q, want %q", got, tt.path)
+			}
+		})
+	}
+}