Add comprehensive test coverage for: - ProxyHostModel: 37 tests for JSON converters and serialization - ContainerModel: 44 tests for deserialization, entity conversion, state parsing - StackModel: 55 tests for type/status parsing, timestamps, entity properties 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>