feat(render3d): gpu.ludic - the seam for a second graphics API, and what the GPU can do

Render state (depth, blending, culling, colour writes, alpha-to-coverage, depth bias,
scissor) and uniforms go through gpu_* / u_* and nowhere else; OpenGL state is cached and
only changes reach the driver. Frames are bit-identical to before at the fixed viewpoints.
R3D_GFX=gl|vk or gpu_request chooses a backend, falling back to OpenGL with a reason.

gpu_caps_probe() asks Vulkan, on Windows, for the 1.3 floor, ray tracing, mesh shaders, the
NVIDIA RTX generation, Reflex and HDR colour spaces, for a game's settings to grey out what
a machine cannot use; R3D_CAPS pretends to be a given card for tests.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

packages/ludic.render3d/programs.ludic

@@ -75,7 +75,7 @@ function r3d_program(vs: string, fs: string, defines: string) -> int {
 function r3d_bind_tex(prog: int, name: string, unit: int, target: int, tex: int) -> void {
   gl_active_texture(GL_TEXTURE0 + unit)
   gl_bind_texture(target, tex)
-  gl_uniform1i(gl_get_uniform_location(prog, name), unit)
+  u_i(gpu_uniform(prog, name), unit)
 }
 function r3d_bind_2d(prog: int, name: string, unit: int, tex: int) -> void { r3d_bind_tex(prog, name, unit, GL_TEXTURE_2D, tex) }