docs: add comprehensive usage, deployment, and performance guides

Add three major documentation files to support production deployment:

- ADVANCED_FEATURES.md: In-depth guide on reservoir computing, MLP
  routing, and SNN wake detection with code examples, integration
  patterns, and configuration tuning (400+ lines)

- DEPLOYMENT.md: Complete deployment guide for Android (JNI), iOS
  (static lib), and Linux mobile platforms with cross-compilation,
  size optimization, and CI/CD setup (500+ lines)

- PERFORMANCE.md: Comprehensive optimization guide covering CPU
  (SIMD, vectorization), memory (pooling, compact structures),
  battery (event-driven, batching), and platform-specific
  optimizations (600+ lines)

These guides complement the existing architecture documentation and
provide practical implementation details for production deployment
on constrained mobile platforms.

Total documentation added: 1,500+ lines

Author: claude