Describe the bug

In pgp/yubikey.go:484-495, string concatenation uses += in a loop:

info += fmt.Sprintf("Manufacturer: %s\n", aid.Manufacturer)
info += fmt.Sprintf("Serial:       %X\n", aid.Serial)
info += fmt.Sprintf("Version:      %s\n", aid.Version)

While not a loop per se, the pattern should use strings.Builder for consistency and performance.

To reproduce

Not a crash but a code quality issue.

Expected behavior

Use strings.Builder for multi-line string construction.