Port Voxy to Minecraft 26.3 (OpenGL)

[PoPoGH]

Ports the 26.2 branch to Minecraft 26.3 with OpenGL rendering. Updates Fabric, Sodium, Iris, Lithium, Mod Menu, Chunky and LWJGL dependencies; migrates graphics references to RenderPearl; adapts the changed Sodium render signatures and model APIs; and replaces GLFW window-handle lookup with SDL.

Compatibility mixins now load only when their optional mod is installed. Obsolete access-widener entries are removed, and non-OpenGL backends disable Voxy before OpenGL initialization.

Validation:

• Java 25 Gradle build and access-widener validation passed.
• Two Windows/NVIDIA in-world smoke tests passed: Sodium alone, and Sodium with Iris 1.11.6 installed (no shaderpack). Each ran for 400 client ticks with a Voxy renderer, then shut down cleanly.
• Includes an opt-in, reproducible smoke-test harness excluded from the production jar.

Limits: Vulkan rendering is not implemented. Shaderpack rendering and Vivecraft/Flashback/Nvidium compatibility have not been validated for 26.3; the latter remain older compile-only integration targets. Visual correctness and longer gameplay sessions still need review.