Tests were failing in CI because they created nodes.enc files without
valid encryption keys, triggering the crypto safety check.
Added createTestEncryptionKey helper and fixed:
- TestLoad_MockEnv (config_load_test.go)
- Multiple tests in commands_test.go that create nodes.enc
Tests were calling Load() without setting PULSE_DATA_DIR, causing them
to try to create /etc/pulse which fails in CI environments.
- Skip TestLoad_Defaults if /etc/pulse doesn't exist
- Add PULSE_DATA_DIR to tests that were missing it