v1.6.0

## [1.6.0] - 2025-10-04

### 🎯 Windows CUDA Support (First in Rust LLM Ecosystem!)

**Issue #72: GPU Backend Flag Implementation + Windows MSVC CUDA**
- ✅ Fixed `--gpu-backend` CLI flag wiring through to model loading
- ✅ **BREAKTHROUGH**: First lightweight Rust LLM tool with Windows MSVC CUDA support
  - Fixed llama-cpp-rs bindgen header discovery issue blocking Windows CUDA builds
  - Uses cc::Build to extract MSVC INCLUDE paths, passes as -isystem to bindgen
  - Fork: Michael-A-Kuykendall/llama-cpp-rs (branch: fix-windows-msvc-cuda-stdbool)
- ✅ Implemented GpuBackend::from_string() parser with helpful error messages
- ✅ Implemented GpuBackend::detect_best() with priority: CUDA > Vulkan > OpenCL > CPU
- ✅ All 4 GPU backends verified on Windows: Vulkan, OpenCL, CUDA, HuggingFace
- ✅ Binary sizes: 4.8MB (minimal), 24MB (CUDA) + 36MB ggml-cuda.lib
- ✅ Build times: HuggingFace 8s, OpenCL 45s, Vulkan 3m19s, CUDA 11m25s

### 🐛 Critical Stability Fixes

**Concurrent Load Deadlock**
- Fixed RwLock deadlock in ModelManager causing infinite hangs with concurrent tasks
- Pattern: Drop write lock immediately after operations, before calling other functions
- All 295 unit tests now passing (was hanging indefinitely at test_concurrent_load_unload)

**Flaky Property Tests**
- Rebuilt 4 property tests without broken property_test() wrapper
- Fixed test_backend_routing_property, test_generation_length_property, etc.
- Tests now deterministic: 284/284 pass minimal features, 295/295 with backends

**Feature Flag Compatibility**
- Added cfg guards to PPT test modules for llama backend features
- Fixed adapter test compilation with minimal features
- All tests work with `--no-default-features --features huggingface`

### Added
- **Opt-in Usage Analytics**: Anonymous business intelligence collection system
- **Performance Benchmarking Tools**: Cross-platform scripts for real GPU/CPU measurement
- **Comprehensive Security Policy**: Private vulnerability disclosure process (SECURITY.md)
- **DCO (Developer Certificate of Origin)**: Legal compliance for all contributions
- **Professional GitHub Templates**: Issue/PR templates with structured workflows
- **Branch Protection**: Quality gates with CI and DCO enforcement
- **Automated Changelog**: CI/CD integration for release documentation

### Changed
- **Enhanced CONTRIBUTING.md**: Added maintainer process and DCO requirements
- **Improved Documentation**: Comprehensive performance analysis and metrics transparency
- **Professional Repository Structure**: Security-first approach with industry standards

### Security
- **Private Security Disclosure**: GitHub Security Advisories integration
- **DCO Compliance**: All contributions legally certified
- **Branch Protection**: Enforced code review and quality gates

### Documentation
- **Performance Analysis**: Real benchmarking tools and GPU consumption data
- **Metrics Transparency**: Complete disclosure of business intelligence collection
- **Contributing Guidelines**: Clear maintainer process and legal requirements