Tests for:
- normalizePoweredOffSeverity: Verifies severity normalization to warning/critical
- cloneMetadata: Deep copy functionality for metadata maps
- cloneMetadataValue: Type-specific cloning for various slice and map types
- Alert.Clone: Full alert cloning with pointer field independence
46 test cases covering nil handling, deep copy verification, slice/map
independence, and all supported metadata value types.
Coverage improved from 44.8% to 45.3%.
