feat(pipeline): implement Asset Pipeline (RF6.5)

[LyeZinho]

@

Summary

Implements the complete Asset Pipeline system for the Caffeine Engine (RF6.5):

• TextureEncoder: Converts raw pixels to .caf format with mipmap generation using box filter
• AudioEncoder: Converts WAV files to .caf format with PCM16 encoding
• MeshEncoder: Converts OBJ files to .caf format using existing MeshLoader
• AssetManifest: JSON-based asset tracking with save/load functionality
• AssetPipeline: Batch processing with incremental build support (CRC-based)
• caf-encode CLI: Command-line tool for texture/audio/mesh/batch conversions

Implementation Details

• All code is header-only (no .cpp for library components)
• Pure C++20 with no external dependencies (no stb_image, dr_wav, cgltf)
• Comprehensive test suite with 28+ tests covering all components
• Follow exact style conventions from existing codebase

Testing

• ✅ All tests pass (28+ tests in test_pipeline.cpp)
• ✅ Builds successfully on MSVC (Windows)
• ✅ No external dependencies required
• ✅ Header-only implementation

Files Changed

New Files:

• src/tools/PipelineTypes.hpp - Core pipeline types
• src/tools/TextureEncoder.hpp - Texture encoding with mipmaps
• src/tools/AudioEncoder.hpp - Audio encoding (WAV support)
• src/tools/MeshEncoder.hpp - Mesh encoding (OBJ support)
• src/tools/AssetManifest.hpp - Asset manifest JSON management
• src/tools/AssetPipeline.hpp - Batch processing pipeline
• tools/caf-encode/main.cpp - CLI tool
• tests/test_pipeline.cpp - Comprehensive test suite

Modified Files:

• CMakeLists.txt - Added caf-encode executable
• src/Caffeine.hpp - Added tools module includes
• tests/CMakeLists.txt - Added test_pipeline.cpp
• docs/fase6/asset-pipeline.md - Updated status to ✅ Implementado

Acceptance Criteria (from RF6.5)

• caf-encode texture converts raw pixels → .caf with mipmaps
• caf-encode audio converts WAV → .caf PCM16
• caf-encode mesh converts OBJ → .caf Mesh3D
• caf-encode batch processes entire directories with parallelization support
• Incremental build support via file timestamp checking
• Asset manifest JSON generation
• Comprehensive test coverage

Related Issues

Closes #41
@