- Add Test effect with operations: assert, assertEqual, assertNotEqual,
assertTrue, assertFalse, fail
- Implement Test effect handlers in interpreter with TestResults tracking
- Add values_equal method for comparing Value types in tests
- Update lux test command to discover and run test_* functions
- Create example test files: test_math.lux, test_lists.lux
- Add TESTING_DESIGN.md documentation
- Fix AST mismatches in C backend and compiler.rs for compatibility
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
