Split reusable code into separate repositories

Current State

Engine/editor has reusable subsystems (GLFS parsing, shader compilation, Vulkan/GPU abstraction) baked directly into the monorepo.

Tasks:

• Extract GLFS (GL Shader) parsing into its own repository
• Extract shader compilation pipeline (Vulkan shaders) into own repo
• Extract basic GPU/Vulkan abstraction layer into own repo
• Follow same pattern as math3d, open-asset-package, and guid extractions
• Update engine/editor to depend on these as external packages (Zig dependencies)
• Ensure CI builds for each extracted repo
• Write docs on how to contribute to each extracted library

Acceptance Criteria:

• GLFS parsing lives in its own repo as a Zig package
• Shader compilation pipeline lives in its own repo
• GPU/Vulkan abstraction layer lives in its own repo
• Each repo has CI, docs, and a Zig build.zig.zon manifest
• Engine/editor depends on them via Zig package dependencies
• Extraction follows the same conventions as math3d, open-asset-package, and guid

Related: