refactor(render3d): programs, GPU timers and the context behind gpu.ludic

The last of milestone 1: no OpenGL call is left in render3d outside gpu.ludic but the clock
and the CPU-side buffer helpers.

- gpu_program builds a program and remembers the variant it came from (vertex, fragment and
  defines as one line - the SPIR-V manifest's key), so a backend that cannot compile at run
  time finds the pipeline for the same handle. gpu_use_program and gpu_program_free replace
  32 uses and 2 frees; the overlay's program is recorded under overlay.vert|overlay.frag.
- gpu_query_new / _begin / _end / _result carry R3D_PROF's timers.
- gpu_open, gpu_vsync, gpu_renderer_name and gpu_resize_check carry the context.
- r3d_program_tess is gone: nothing called it and no tessellation shader exists.
- R3D_GLCHECK also checks after framebuffer and renderbuffer changes, viewport, draw buffers,
  program use, texture parameters, the resize check and between frames.

OpenGL frames are byte-identical at the five viewpoints; 59 self-tests pass with and without
R3D_GLCHECK, with no GL error; ludic-dev test 140 passed.

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

packages/ludic.render3d/sky.ludic

@@ -74,7 +74,7 @@ function sky_convolve(prog: int, target_tex: int, layer: int, w: int, h: int, ro
   if layer < 0 { gpu_fb_color(0, target_tex) }
   else { gpu_fb_color_layer(0, target_tex, layer) }
   gpu_viewport(0, 0, w, h)
-  gl_use_program(prog)
+  gpu_use_program(prog)
   r3d_bind_2d(prog, "u_sky", 0, sky_tex)
   sky_bind_rot(prog)
   u_f(gpu_uniform(prog, "u_sun_clip"), hdr_clip)