Fixed the first five errcheck linter errors:
- Added error handling for os.Unsetenv in cli_test.go
- Added error handling for file.Close() in crypto.go (4 instances)
- Convert for loops to use Go 1.22+ integer ranges in generate.go and helpers.go
- Disable G101 false positives for test vectors and environment variable names
- Add file-level gosec disable for bip85_test.go containing BIP85 test vectors
- Add targeted nolint comments for legitimate test data and constants