fix: remove unused error return from getCurrentBranchOrHEAD

The function always returns nil for error since it is designed to
return HEAD on detached HEAD state. Simplify signature to just
return string.

Fixes golangci-lint unparam warning.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/sync_branch.go

@@ -25,13 +25,13 @@ func getCurrentBranch(ctx context.Context) (string, error) {
 // getCurrentBranchOrHEAD returns the current branch name, or "HEAD" if in detached HEAD state.
 // This is useful for jj/jujutsu compatibility where HEAD is always detached but we still
 // need a reference for git operations like log and diff.
-func getCurrentBranchOrHEAD(ctx context.Context) (string, error) {
+func getCurrentBranchOrHEAD(ctx context.Context) string {
 	branch, err := getCurrentBranch(ctx)
 	if err != nil {
 		// Detached HEAD - return "HEAD" as the reference
-		return "HEAD", nil
+		return "HEAD"
 	}
-	return branch, nil
+	return branch
 }
 
 // getSyncBranch returns the configured sync branch name
@@ -59,10 +59,7 @@ func showSyncStatus(ctx context.Context) error {
 		return fmt.Errorf("not in a git repository")
 	}
 
-	currentBranch, err := getCurrentBranchOrHEAD(ctx)
-	if err != nil {
-		return err
-	}
+	currentBranch := getCurrentBranchOrHEAD(ctx)
 
 	syncBranch, err := getSyncBranch(ctx)
 	if err != nil {