Add comprehensive test suite

[LynnColeArt]

Build test coverage for reliability:

• Unit tests for each module
• Integration tests for device interaction
• Stress tests for mesh stability
• Performance regression tests
• Multi-device scenario tests

Tests should run on diverse hardware configurations.

[LynnColeArt]

Significant test coverage added:

• ✅ Unit tests for core modules (kinds, memory, platform)
• ✅ Integration tests for conv2d operations
• ✅ Performance benchmarks with detailed timing
• ✅ Multi-device tests (CPU vs GPU)
• ✅ PM4 leak tests (1000x allocation cycles)
• ✅ Integrity checks via Mini's pre-commit hooks

Still TODO:

• Automated CI pipeline to run tests
• Stress tests for mesh stability
• More edge case coverage

This issue is about 70% complete.