fix: support git worktrees in hooks installation

Use `git rev-parse --git-dir` instead of hardcoded `.git` path to find
the actual git directory. In worktrees, `.git` is a file containing a
gitdir pointer, not a directory.

Changes:
- Add getGitDir() helper in hooks.go
- Update installHooks(), uninstallHooks(), CheckGitHooks() to use it
- Update hooksInstalled(), detectExistingHooks(), installGitHooks() in init.go
- Update checkHooksQuick() in doctor.go
- Update GitHooks() in doctor/fix/hooks.go
- Update tests to use real git repos via `git init`

Fixes bd-63l

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

cmd/bd/hooks.go

@@ -13,6 +13,18 @@ import (
 	"github.com/spf13/cobra"
 )
 
+// getGitDir returns the actual .git directory path.
+// In a normal repo, this is ".git". In a worktree, .git is a file
+// containing "gitdir: /path/to/actual/git/dir", so we use git rev-parse.
+func getGitDir() (string, error) {
+	cmd := exec.Command("git", "rev-parse", "--git-dir")
+	output, err := cmd.Output()
+	if err != nil {
+		return "", fmt.Errorf("not a git repository: %w", err)
+	}
+	return strings.TrimSpace(string(output)), nil
+}
+
 //go:embed templates/hooks/*
 var hooksFS embed.FS
 
@@ -46,13 +58,23 @@ func CheckGitHooks() []HookStatus {
 	hooks := []string{"pre-commit", "post-merge", "pre-push", "post-checkout"}
 	statuses := make([]HookStatus, 0, len(hooks))
 
+	// Get actual git directory (handles worktrees)
+	gitDir, err := getGitDir()
+	if err != nil {
+		// Not a git repo - return all hooks as not installed
+		for _, hookName := range hooks {
+			statuses = append(statuses, HookStatus{Name: hookName, Installed: false})
+		}
+		return statuses
+	}
+
 	for _, hookName := range hooks {
 		status := HookStatus{
 			Name: hookName,
 		}
 
 		// Check if hook exists
-		hookPath := filepath.Join(".git", "hooks", hookName)
+		hookPath := filepath.Join(gitDir, "hooks", hookName)
 		version, err := getHookVersion(hookPath)
 		if err != nil {
 			// Hook doesn't exist or couldn't be read
@@ -276,10 +298,10 @@ var hooksListCmd = &cobra.Command{
 }
 
 func installHooks(embeddedHooks map[string]string, force bool, shared bool) error {
-	// Check if .git directory exists
-	gitDir := ".git"
-	if _, err := os.Stat(gitDir); os.IsNotExist(err) {
-		return fmt.Errorf("not a git repository (no .git directory found)")
+	// Get actual git directory (handles worktrees where .git is a file)
+	gitDir, err := getGitDir()
+	if err != nil {
+		return err
 	}
 
 	var hooksDir string
@@ -338,7 +360,12 @@ func configureSharedHooksPath() error {
 }
 
 func uninstallHooks() error {
-	hooksDir := filepath.Join(".git", "hooks")
+	// Get actual git directory (handles worktrees)
+	gitDir, err := getGitDir()
+	if err != nil {
+		return err
+	}
+	hooksDir := filepath.Join(gitDir, "hooks")
 	hookNames := []string{"pre-commit", "post-merge", "pre-push", "post-checkout"}
 
 	for _, hookName := range hookNames {