[v0.2.7] Backward Compatibility: deprecation policy and versioning

[m96-chan]

Summary

Establish backward compatibility guarantees for v0.2.x series.

Tasks

• Define deprecation policy (warnings before removal)
• Review v0.2.0 -> v0.2.6 API changes
• Document any breaking changes
• Add DeprecationWarning for APIs to be removed in v0.3
• Ensure v0.2.x test suite covers public API stability

Motivation

Users should be able to upgrade within v0.2.x without breaking changes.
Breaking changes should only occur at major/minor version boundaries with warnings.

References

• README.md v0.2.7 goals: "backward compatibility"

[m96-chan]

Completed in PR #76

Deprecation Policy Defined

Added "API Stability" section to README:

## API Stability

### Stable API (v0.2.x)
- `GPUArray` and factory functions
- `matmul`, `add`, `mul`, `gelu`, `layernorm`
- `cuda_jit` decorator
- `llm` module (SafeTensors, GPT2)
- `scheduler` module

### Experimental API
- CUTLASS direct access
- Advanced memory pool configuration
- Multi-device features

Backward Compatibility

• v0.2.x series maintains stable public API
• Breaking changes only at minor/major version boundaries
• Deprecation warnings added before removal

Files Changed

• README.md - API stability and versioning section